Results 1 to 6 of 6

Math Help - Perfect Square Trinomial

  1. #1
    Member
    Joined
    Dec 2007
    Posts
    96

    Question Perfect Square Trinomial

    Find two values of b that will make [tex]9x^2+bx+25[tex] a perfect square trinomial.

    The formulas for Perfect Square Trinomial are:
    [tex](a+b)^2=a^2+2ab+b^2[tex]
    [tex](a-b)^2=a^2-2ab+b^2[tex]

    As I solved:

    [tex]9x^2+bx+25[tex]
    [tex](3x)^2+2(3x)(5)+5^2[tex]
    [tex]9x^2+6x(5)+25[tex]
    [tex]9x^2+30x+25[tex]

    Then...according to this one of those two values would be 30 but I'm not sure about it for I didn't find anything. I just replaced the given values [tex]9x^2[tex] and [tex]25[tex] into the middle term of the formula. And I couldn't find the other number.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Alienis Back View Post
    Find two values of b that will make [tex]9x^2+bx+25[tex] a perfect square trinomial.

    The formulas for Perfect Square Trinomial are:
    [tex](a+b)^2=a^2+2ab+b^2[tex]
    [tex](a-b)^2=a^2-2ab+b^2[tex]

    As I solved:

    [tex]9x^2+bx+25[tex]
    [tex](3x)^2+2(3x)(5)+5^2[tex]
    [tex]9x^2+6x(5)+25[tex]
    [tex]9x^2+30x+25[tex]

    Then...according to this one of those two values would be 30 but I'm not sure about it for I didn't find anything. I just replaced the given values [tex]9x^2[tex] and [tex]25[tex] into the middle term of the formula. And I couldn't find the other number.
    (3x + 5)^2 = ...... So b = 30 is correct.

    (3x - 5)^2 = ..... So b = .......
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Dec 2007
    Posts
    96

    Just one more question

    Why didn't it show the problem without the tags...mmm...I mean this "[tex]" things. I'd like to learn how to write problems using them. Is there any thread on the subject?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Alienis Back View Post
    Why didn't it show the problem without the tags...mmm...I mean this "[tex]" things. I'd like to learn how to write problems using them. Is there any thread on the subject?
    (a+b)^2=a^2+2ab+b^2
    (a-b)^2=a^2-2ab+b^2

    come from [tex](a+b)^2=a^2+2ab+b^2[/tex] and [tex](a-b)^2=a^2-2ab+b^2[/tex].

    See http://www.mathhelpforum.com/math-help/latex-help/
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Dec 2007
    Posts
    96

    Let's see if it works...

    Find two values of b that will make 9x^2+bx+25 a perfect square trinomial.

    The formulas for Perfect Square Trinomial are:
    (a+b)^2=a^2+2ab+b^2
    (a-b)^2=a^2-2ab+b^2

    As I solved:

    9x^2+bx+25
    (3x)^2+2(3x)(5)+5^2
    9x^2+6x(5)+25
    9x^2+30x+25

    Then...according to this one of those two values would be 30 but I'm not sure about it for I didn't find anything. I just replaced the given values 9x^2 and 25 into the middle term of the formula. And I couldn't find the other number.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member
    Joined
    Dec 2007
    Posts
    96
    WOW...That's Great!!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. perfect square trinomial/square of binomial
    Posted in the Algebra Forum
    Replies: 2
    Last Post: March 3rd 2011, 05:02 PM
  2. Replies: 1
    Last Post: July 21st 2010, 03:24 PM
  3. Replies: 5
    Last Post: November 6th 2009, 06:08 PM
  4. Replies: 1
    Last Post: September 13th 2009, 12:24 PM
  5. Replies: 5
    Last Post: March 22nd 2008, 06:28 PM

Search Tags


/mathhelpforum @mathhelpforum