Results 1 to 5 of 5

Math Help - Trinomials

  1. #1
    Newbie
    Joined
    Jul 2005
    Posts
    6

    Question Trinomials

    the following trinomial given to us:

    Find all the integer values for b so that the trinomial can be factored how do I do this can you show your work please!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    hpe
    hpe is offline
    Member hpe's Avatar
    Joined
    Apr 2005
    Posts
    158
    Quote Originally Posted by leleirvin
    the following trinomial given to us:

    Find all the integer values for b so that the trinomial can be factored how do I do this can you show your work please!
    You have to tell us what the trinomial is.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jul 2005
    Posts
    6

    sorry

    3x^2 +bx +2
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Senior Member
    Joined
    Jun 2005
    Posts
    295
    Awards
    1
    This particular trinomial is a quadratic. There are lots of ways to factor a quadratic: note that factoring it into two linear factors is the same as finding the two roots of the equation formed by setting it equal to zero.

    One way is as follows. Suppose 3x^2 + bx + 2 = (px+q)(rx+s) with p,q,r,s integers. Then pr = 3 and qs = 2. That is, p=3,r=1 or p=1,r=3 or p=-3,r=-1 or p=-1,r=-3; similarly q=2,s=1 or q=1,s=2 or q=-2,s=-1 or q=-1,s=-2. The value of b is ps+qr which is therefore one of 7,5,-7,-5.

    Another way is as follows, Solve the quadratic to give x = (-b +- sqrt(b^2-24) ) / 12. We need b^2-24 to be a perfect square, say d^2. If b^2-24 = d^2 then b^2-d^2 =24, so (b+d)(b-d)=24. The possibilities for b+d,b-d respectively are 24,1 or 12,2 or 8,3 or 6,4 or 4,6 or 3,8 or 2,12 or 1,24 or -24,-1 or ... -1,-24. Again we find that the integral values of b are 7,5,-5,-7.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jul 2005
    Posts
    6

    Thanks

    I truly love this site it has helped me so much this book can be very confuseing at times ,but you guys explain so well and much better than my book. Having to teach myself math is hard. And being online for math class is even harder! Thanx; keep up the great work!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. factoring trinomials
    Posted in the Algebra Forum
    Replies: 2
    Last Post: September 12th 2010, 04:51 AM
  2. Trinomials
    Posted in the Algebra Forum
    Replies: 2
    Last Post: September 15th 2009, 03:20 PM
  3. Factoting Trinomials
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 21st 2009, 09:55 AM
  4. Trinomials
    Posted in the Algebra Forum
    Replies: 1
    Last Post: March 27th 2009, 07:41 AM
  5. Factorising Trinomials
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 31st 2009, 06:22 PM

Search Tags


/mathhelpforum @mathhelpforum