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Variables - College Algebra

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    Actually, as much as it might surprise
    you, we've been doing algebra right here.
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    These 2 symbols, the square and the
    triangle that we assigned to replace the
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    words that we had written earlier are
    called variables. In algebra we make a
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    distinction between numbers and variables.
    Numbers are well, numbers, like 3,000,000
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    or 100,000, and variables are generally
    represented by symbols or single letters.
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    A variable doesn't have a set value like a
    number does. Instead, it's value is
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    allowed to vary depending on what we
    decide that it should equal. We'll talk more
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    about how we make decisions about that
    soon. Numbers will appear either as
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    constant terms on their own, just numbers
    like 3,000,000 right here, or in terms
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    that combine numbers and variables like
    this last one on the right. When
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    multiplied by a variable or set of
    variables, a number is called a
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    coefficient. So again, going back to our
    variables, I could of chosen any two
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    symbols I wanted to represent these two
    quantities right here, the square and the
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    triangle. I didn't have to choose the
    triangle and I didn't have to choose the
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    square. In fact picking these two
    particular symbols, is actually pretty
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    unconventional in math. To give you a
    preview of what you're usually going to be
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    seeing during this course, I'll write this
    equation out with more typical notation.
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    We'll most often see the letters X and Y
    as your variables in equations in algebra.
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    You can also see I've removed the dollar
    signs and the commas from the original
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    equation down here to make this equation
    look a little bit more clean and strictly
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    mathematical. You'll notice that I also
    sneakily deleted the multiplication sign
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    we had in the top equation, and didn't
    write it down here at the bottom. When we
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    have single terms that involve both
    numbers and variables multiplied together,
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    we don't usually write the multiplication
    sign in, like I did at the top. As long as
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    we write the symbols directly next to each
    other, with nothing in between,
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    multiplication is assumed to be happening
    between them. It's like there's an
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    invisible multiplication sign written
    right here. I'm going to erase that
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    though, to remind us that we're not
    usually going to see any multiplication
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    signs written between numbers and
    variables. Although people doing math
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    often use the variables y and x in their
    equations, I really want you to remember
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    that this is not necessary. Triangles and
    squares are just as useful as x's and y's.
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    No matter what symbol you choose to write
    a variable with, the power that it has is
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    still the same. It acts as a slot where we
    can insert different numbers to make terms
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    and expressions take on different values.
    So maybe I set this first variable equal
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    to 3 and the second equal to -1 or
    maybe this is -1/2 and this is 23.
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    In certain situations, there will be
    restrictions placed on what different
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    variables can equal. But, until we have
    more information about what they equal, we
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    leave them written as variables, showing
    that their values are still sort of a
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    mystery to us.
Cím:
Variables - College Algebra
Video Language:
English
Team:
Udacity
Projekt:
MA008 - College Algebra
Duration:
02:53

English subtitles

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