algebra

Can someone please help me with the following?:

Factor each expression completely:

x²-x-72

3x²-3x-168

Here is the way I have found to do these. First, make a couple of sets of parentheses.
( )( )
We put in the first letter. From X2 we can get ONLY X and X so put those in.
(X )(X ).
We next see that both of the signs are negative; therefore, the ONLY way we can get that is to have one of them + and one - so we put those in.
(X+ )(X- ).
The last number is done this way. Think of factors of 72 that multiply to give 72 but add (or subtract in this case) to give 1. Factors of 72 are 2*36; 3*24; 4*18; 6*12; 8*9. The ONLY one of those that has a chance of working is the last one BECAUSE, while all of them multiply to give 72, only the last set has a difference of 1 between the two. So we use 8 and 9 as the last numbers in the parentheses and place it so that the larger number gives a minus sign.
(X+8)(X-9) = X2-x-72. Now you try the last one and see if this doesn't work ok. Hint: I think 3 is a common factor so I would start with
3(X2-x-56) and factor the simpler set of numbers. Post your work if you get stuck and please tell us where you are having trouble. These can be daunting, at first, but practice, practice, and that makes things better.

1) x^2 -x-72 = (x-9)(x+8)
2) 3x^2 -3x-168 = 2(x^2 -x-56) --> (x-8)(x+7)

Thank you. I have the first figured out. But for the 2nd one, would it be (x-8)(x+7) or (3x-24)(3x+21)? Because I did x(squared)-x-56 to get (x-8)(x+7), but then don't you have to multiply it by the 3?

Nevermind, I understand it. It would be (x-8)(x+7) because you divided by the 3 to get 56. So, thanks!!!

I understand. Thank you!

  1. 👍 0
  2. 👎 0
  3. 👁 150

Respond to this Question

First Name

Your Response

Similar Questions

  1. math

    Completely factor the expression 2a3 − 128. A. 2(a − 4)3 B. 2(a − 4)(a2 + 4a + 16) C. 2(a3 − 64) D. Prime Completely factor the expression 7(x − y) − z(x − y). A. Prime B. (x − y)(7 − z) C. (x − y)(7 + z) D. (x

    asked by realiesna on May 14, 2015
  2. math

    Completely factor the expression 16t3 − 50t2 + 36t. A. 2t(8t − 9)(t − 2) B. Prime C. 2t(8t + 9)(t + 2) D. 2t(8t − 25t + 18) Completely factor the expression 48u4v4 − 18u2v2 − 3u8v5. A. Nonfactorable B. 3u2v2(16u2v2 −

    asked by Kenny D on May 14, 2015
  3. math

    Completely factor the expression 16t3 − 50t2 + 36t. A. 2t(8t − 9)(t − 2) B. Prime C. 2t(8t + 9)(t + 2) D. 2t(8t − 25t + 18) Completely factor the expression 48u4v4 − 18u2v2 − 3u8v5. A. Nonfactorable B. 3u2v2(16u2v2 −

    asked by tina on May 14, 2015
  4. math

    Trying to factor 2 equations 3x2+9x-30 4x2-4x-48 I assume you mean 3x² + 9x - 30 which on this board most people write as 3x^2 ... =3(x^2 + 3x - 10) =3(x+5)(x-2) do the same thing for your second question, factor out the 4 first,

    asked by Chris on April 18, 2007
  5. Algebra 2

    1.) The cost in C dollars of manufacturing x bicycles at Holliday's Production Plant is given by the function C(x) = 2x2 - 800x + 92,000. Find the minimum cost. 2.) The vertex of y = -3x2- 6x - 9 lies in which quadrant? 3.) Given

    asked by Becka on February 27, 2014
  6. please help me(math)

    4x^2+20x+5y+xy *you have top factor by grouping.If you need more info just ask me but please help me!!!* An example from http://www.ltcconline.net/greenl/courses/152b/FactoringRatExpr/factor.htm Factoring by Grouping Consider the

    asked by margie on January 23, 2007
  7. factoring

    I cannot figure these out.Can someone Factor completely: 3x2 - x - 4 I suppose this is actually 3x^2 -x-4 If so: (3x-4)(x+1) Now I'd like you to look at the following website:

    asked by Jojo on May 23, 2007
  8. Algebra 2

    Can this expression be factored? 4x^2+9 My homework assignment says to factor completely and this is one of the problems but I don't think this expression can be factored. Am I wrong? If so how do I factor it.

    asked by Judy on October 2, 2015
  9. math

    Factor each expression completely: 18b²+24b-10 Thanks in advance. factor out a two first, then 2*(9b^2 + 12b -5) 2(3b+5)(3b-1)

    asked by Lola on November 13, 2006
  10. algbera

    if possibly completely factor the factor the expression(if the polynomial is not factorable using integers enter prime) x^2+10x+16

    asked by missfubu-c on October 18, 2012

More Similar Questions