Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: How do I factor 3x-3y-x^2+y^2

  1. Apr 1, 2012 #1
    My textbook says the answer is (3-x-y)(x-y)

    I tried to factor it two different ways. One time I got
    And the other time I got

    I've never seen a polynomial with 4 unlike terms like this before, and I am not understanding how 3-x-y is part of the answer (it has three terms in it). How does one go about factoring something like this?
  2. jcsd
  3. Apr 1, 2012 #2


    User Avatar
    Homework Helper

    Hint: 3x-3y = 3(x-y)


    -x^2 + y^2 = -(x^2 - y^2) = -(x+y)(x-y)

    EDIT: Nice April Fool's joke, Evo. I love that avatar. Think I'll keep her.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook