Results 1 to 3 of 3

Math Help - binomial

  1. #1
    Junior Member
    Joined
    Mar 2008
    Posts
    54

    binomial

    I need to factor this completely:

    16x^2 - (y + 3)^2

    <br />
16x^2 - (y + 3)^2<br />
= [16x - (y+3)]^2<br />
= [4x - (y+3)]^2<br />
= (2x - y - 3)(2x + y + 3)

    but the answer in the packet says:

    (4x + y + 3)(4x - y - 3)

    My answer differs from the one in the packet at the last step. Is it because I cannot turn 16x into 4x?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Apr 2008
    Posts
    1,092
    Quote Originally Posted by lax600 View Post
    I need to factor this completely:

    16x^2 - (y + 3)^2

    <br />
16x^2 - (y + 3)^2<br />
= [16x - (y+3)]^2<br />
= [4x - (y+3)]^2<br />
= (2x - y - 3)(2x + y + 3)

    but the answer in the packet says:

    (4x + y + 3)(4x - y - 3)

    My answer differs from the one in the packet at the last step. Is it because I cannot turn 16x into 4x?
    You're just not correctly converting the difference of squares. We have:

    16x^2 = a^2

    (y+3)^2 = b^2

    Hence, a = 4x and b = y + 3.

    So, using the formula a^2 - b^2 = (a + b)(a - b) we have:

    (4x + y + 3)(4x - y - 3).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2008
    Posts
    54
    Oh! Alright thanks ^^
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: July 15th 2010, 06:33 AM
  2. Replies: 1
    Last Post: November 12th 2009, 01:38 AM
  3. Binomial Theorem or Binomial Coefficient
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: October 2nd 2009, 02:06 PM
  4. Replies: 1
    Last Post: March 12th 2009, 12:09 AM
  5. Relation between Negative Binomial and Binomial Distros
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: November 5th 2007, 07:59 AM

Search Tags


/mathhelpforum @mathhelpforum