Results 1 to 2 of 2

Math Help - function help..

  1. #1
    Junior Member
    Joined
    Mar 2007
    Posts
    45

    function help..

    My homework is due within the hour online, and I can't seem to figure out this problem..


    It says Evaluate F(3x+5)if f(x)=2x^2+2x+3

    Now in the solutions manual it gives the follwing steps

    f(3x+5)=2(3x+5)^2+2(3x+5)+3

    = 2(9x^2+30x+25)+6x+10+3

    =18x^2+66X+63

    I get the whole problem except for- how did they get the 30x in the 2nd step? Can someone please tell me how they got the 30x? Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Apr 2006
    Posts
    401
    Quote Originally Posted by Mathfailure View Post
    My homework is due within the hour online, and I can't seem to figure out this problem..


    It says Evaluate F(3x+5)if f(x)=2x^2+2x+3

    Now in the solutions manual it gives the follwing steps

    f(3x+5)=2(3x+5)^2+2(3x+5)+3

    = 2(9x^2+30x+25)+6x+10+3

    =18x^2+66X+63

    I get the whole problem except for- how did they get the 30x in the 2nd step? Can someone please tell me how they got the 30x? Thanks!
    2(3x+5)^2 = 2*[9x^2 + 30x + 25]

    Expand (3x + 5)^2, and you'll see it is 9x^2 + 30x + 25...

    (3x + 5)*(3x + 5) = 9x + 15x + 15x + 25 (using FOIL).
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 20
    Last Post: November 27th 2012, 06:28 AM
  2. Replies: 0
    Last Post: October 19th 2011, 05:49 AM
  3. Replies: 4
    Last Post: October 27th 2010, 06:41 AM
  4. Replies: 3
    Last Post: September 14th 2010, 03:46 PM
  5. Replies: 2
    Last Post: September 2nd 2010, 11:28 AM

Search Tags


/mathhelpforum @mathhelpforum