Got a YouTube account?

New: enable viewer-created translations and captions on your YouTube channel!

English subtitles

← Factoring Practice 3 - Visualizing Algebra

Get Embed Code
1 Language

Showing Revision 3 created 05/25/2016 by Udacity Robot.

  1. For this trinomial, we want to find factors of a hundred, that sum to negative
  2. 20. We get the hundred from multiplying 25 times four. These are the factor
  3. pairs for positive 100. But remember that this is positive 100, and I have a
  4. negative 20 down here. We need to find factors of positive 100 that sum to
  5. negative 20. This must mean that our factor pair must contain two negative
  6. numbers. So negative ten and negative ten must be the answers here. They
  7. multiply to give us positive 100 and they sum to negative 20. But before I go to
  8. do this step, I should have asked myself first, is there a GCF here? Well two
  9. doesn't go into every number because this one's not even. They don't all share
  10. an x, and there's no other common factors for 4, 20 and 25 besides one, so I can
  11. continue factoring as usual. We can factor 5x from the first two terms and a
  12. negative two from the second two terms. Completing my factoring by grouping, I
  13. have 5x minus 2 times 5x minus 2. Since it's factors repeated, I can simply
  14. write it with a square. Here's my complete factored form. Some of you might have
  15. taken a shortcut. You might have recognized this as a special pattern. Our first
  16. term and our last term are perfect squares. So this fits our perfect square
  17. trinomial pattern. We can just write out answer as 5x minus 2 squared. The a is
  18. 5x and the b is 2.