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Translator: Hong Yun Lim 임홍윤

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우리는 CST 를 곧 치를거에요

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Algebra 1 (대수학 1 ) 기출문제

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저번에는 Algebra 2 (대수학 2 ) 를 끝냈어요

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거꾸로(역순으로) 할꺼에요

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첫번째 문제를 가져다 붙일게요

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이게보기좋네요

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카피했구요

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열로옮길게요

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자됬네요.

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자됬네요

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문제가묻는것은 3 X 2x -4

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는 -18 가 6x -12 =18 일때 어떤법칙을사용했냐를 묻고있어요

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자생각해봐요

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이걸 3 으로나누면 어떻게되죠?

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3곱하기 2x 는 6x

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3 곱하기 -4 는 -12

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그때 이건당연히 18이죠

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그러무로 이건같은거니

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만약 니가 3을 분배법칙을사용해 3x -4 를 곱하면

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그러면 6x -12 가나오죠

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그러므로 답은 맞다에요

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이건아니고요

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묻고있어요

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덥셈공식을사용했나?

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아니죠

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결합법칙?

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아니죠

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분배버칙을사용했나?

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[소방차 사이렌 소리]

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바깥에서 소방차가 지나가군요.

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자보조

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아 어디있지?

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오 여기있다

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이건 분배법칙이사용된거에요

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곱셈법칙이사용된

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이게맞아요

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저희는 3 을 2x-4에분배했죠

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그리고 왜덥셈이냐면

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+(-4) 가있으니까요

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덥셈과 뺄셈은 같은거에요

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당신이 분배법칙을사용할때

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어쨌든 다음문제로넘어가죠

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다음문제는 여기있어요

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문제 2

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루트 16과 8^1/3 를 더하면

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뭐냐고 물어보고있어요

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루트 16 이뭐죠?

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루트가있으면

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이건 플러스마이너스 4 죠

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여기선 그냥 4

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그들이필요하면 + - 를 붙일거에요

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- 루트

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지금은 4에요 그러면이제 8^1/3 은 ?

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이건 2^3은 8 맞죠?

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2^3= 8 인걸알죠이제

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같은거에요, 8^1/3은

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2에요

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이걸 8 ^1/3 이라고해도되요

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8^1/3 은 2 그러므로 4 더하기 2 은

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6에요 그러므로 B

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문제 3

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----

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좀만내릴게요

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자 이제됬고 같다

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붙이면

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----

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됬다

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이들은알구싶어하는게 x

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x의 6등 곱하기 x 제곱이뭐냐고묻고있어요

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x의 6승과 x 제곱은 같은

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밑을가지고있어요

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이걸곱하면

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지수를더하면되요

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6더하기 2는 8이므로

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여기보면

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x 의 8승을찾아요

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그래서 지수를 더해서 8이나오는걸찾으면

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4더하기 3 은 7

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5더하기 3 은 8

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그러므로 답은 B

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다음문제, 문제 4

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이걸 가져다

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붙이면

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-----

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됬어요

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역수가 없는 수가뭔지 묻고있어요

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-1 의 역수는 -1 /1 이니깐

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-1

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0의 역수는

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1/0 은 정의되지않죠

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그러니깐 답은 B

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0

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1/0 인지 우리는알수없어요

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우리가 생각해봐야할지도.

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그것이 무엇을 의미하는 가 하면

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이것들은 역수가있죠

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1 / 1000 은 1/1000

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따라서 역수는 1000

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3의 역수는 1/3

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다음문제

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----

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여러가지 용어가있네요

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좋아요

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여기로 가져올게요

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다음것도 할것같아요

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----

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좋아요

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여기다둘게요

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-----

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좋아요

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1/2 의multiplicative inverse를 알고싶어요
Multiplicative inverse 는 곱했을떄 1 을만드는수

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1/2 를 뭐랑곱해야

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1이나오죠?

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----

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1/2 의 역수와같아요

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1/2 역수니깐

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1/(1/2)

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이건 2*1 이랑같아요

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따라서 2

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2 곱하기 1/2 는 1

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그래서 답은 2에요

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답은 D

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6번 문제

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이 방정식의 답이뭔가

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절대값기호가있어요

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그냥 잘생각하면되요

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되요

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2x-3 이 절대갑이 5면

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뭘알수있죠?

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2x-3 =5 맞죠?

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이안에있는값이 5면

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ㅣ5ㅣ= 5

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말이되죠

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하지만 그게

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여기다 붙이면

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이게 -5 면

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절대값기호를 씌우면

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5곘죠?

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그래서 2x-3 은 5가될수도있어요

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이걸보면

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5나-5 란걸

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알수있어요

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이걸다시풀면

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3을 양변에더하고

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2x=9

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x=4

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3을 양변에더해요

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2x=-5+3 =-2

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x 는 -1이에요

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따라서 x는 -1 이거나

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4에요 정답은 C

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다음문제

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algebra 1문제는 algebra 2 문제들보다 빨리풀수있어요

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알수있조

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이걸지울게요

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---

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이걸 적을게요

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부등식의 5-

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5-ㅣx+4ㅣ는 -3 보다

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작거나 같데요

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그럼이제

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방금전에한것처럼

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5르배내고

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이방식으로해봐요

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약분할게요

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갔거나작다

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이것보다

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이 5를 얻고싶죠

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양변에 하거나

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부등식

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양변에 하면되요

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5를 양변에서뺴고

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양변에 서 5 를빼면 이 5는사라지죠

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이제 제가 뺄게요

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-5+ 그리고 여기서도 5 를 뺄게요

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----

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그럼 + 가되조

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-5+5 =0, 따라서

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-lxl+4 _< -3-5

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-3-5=-8

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-3-5=-8

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좋아요 다음 에할거는

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부등식부호를 부치고

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그거알아요?

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양변을 -1으로 나누거나 고

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곱하면

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부호가 바꿔요

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그러니깐부등식에서는 음수로 양변을곱하거나하면

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부호가 바뀌조

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그러니깐 제가지금 양변을

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-1 으로 곱하면

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-x +4 기호를바꾸고

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이건 -8 보다 크거나 같다가 되조

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-1 곱했쪼

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-1 으로 곱하면

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-가 없어지고

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x+4는 크거나 같다

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8

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여기서 당연한걸볼수있조

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마지막문제

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뭘말해주조?

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x+4의 크기가

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8보다 크거나 작데요

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수직선을그릴게요

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크기란

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여기서 보면

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길이나 절대값이란소리죠

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여기가 0 이조

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0 이여기있고 8 은여기있어요

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-8 은여기있조 여기서 절대값은

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8보다크데요

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따라서 이 길이가 8 보다 크면되조

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0부터 여기까지라고 해도되요

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8보다 크거나 같다

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1

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그값이 8 보다 크거나 같으면되조

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작은것들은제외한

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모든 값이되조 맞죠?

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크기를 말하는거니

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방향은신경쓰지마요

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크기가 8 보다큰거니

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-8 도 포함되요 (크기는 8 )

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말이되요?

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-9

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00:10:20,160 --> 00:10:22,580
-9의 절대값은

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00:10:22,580 --> 00:10:29,440
9조 그러니깐

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00:10:29,440 --> 00:10:32,340
조건을만족시켜요

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00:10:32,340 --> 00:10:34,380
그러니깐 8부터 오른쪽 끝까지

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이수신이 뭘말해주조?

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00:10:36,540 --> 00:10:39,890
X+4는

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00:10:39,890 --> 00:10:41,235
8보다 크거나 작단소리조

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00:10:41,235 --> 00:10:44,140
이걸적조

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00:10:44,140 --> 00:10:45,710
여기다적을게요

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x+4 는 8보다 크거나작다

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생각해보조

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00:10:51,010 --> 00:10:53,670
크기가 8 보다 크거나 같으니깐

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00:10:53,670 --> 00:11:00,160
아니면 x+4는 -8 보다 작거나크다

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00:11:00,160 --> 00:11:02,060
여기서 왼쪽까지

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-8 부터

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이걸풀었어요

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00:11:05,570 --> 00:11:08,050
여기서 절대값은주요해요

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00:11:08,050 --> 00:11:10,450
헷갈리면안되요

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00:11:10,450 --> 00:11:11,250
한번 확인해보조

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00:11:11,250 --> 00:11:13,630
수직선을 그리면

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00:11:13,630 --> 00:11:18,000
0

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00:11:18,000 --> 00:11:20,150
0부터의 거리가

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00:11:20,150 --> 00:11:23,330
8보다 크거나 같아야하고

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00:11:23,330 --> 00:11:27,310
-8보다 작거나같아한다

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00:11:27,310 --> 00:11:31,150
같을수도있조

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00:11:31,150 --> 00:11:32,420
자 풀어보조

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00:11:32,420 --> 00:11:35,000
x+4 >_ 8

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00:11:35,000 --> 00:11:38,250
4를 양변에빼면

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00:11:38,250 --> 00:11:39,480
x>_4

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00:11:39,480 --> 00:11:41,440
-4 를 양변에서뺀거에요

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00:11:41,440 --> 00:11:44,920
그럼다시

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00:11:44,920 --> 00:11:47,570
아니면 12 와같다

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00:11:47,570 --> 00:11:51,700
따라서 답은 x는4 보다 크거나 같고

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00:11:51,700 --> 00:11:55,510
x는 12 보다 작거나 같다

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따라서 답은D

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00:11:57,860 --> 00:11:59,420
다음비디오에서봐요

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00:11:59,420 --> 00:12:01,400
역자: Hong Yun, Lim