SOLUTION: For what value of k, -4 is a zero of the polynomial x2 – x – (2k + 2)?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: For what value of k, -4 is a zero of the polynomial x2 – x – (2k + 2)?      Log On


   

Question 757610: For what value of k, -4 is a zero of the polynomial x2 – x – (2k + 2)?
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2+%96+x+%96+%282k+%2B+2%29=0
if x=-4
%28-4%29%5E2+%96+%28-4%29+%96+%282k+%2B+2%29=0
16+%2B4+%96+2k-+2=0
16+%2B4-2=2k
18=2k
18%2F2=k
highlight%28k=9%29
x%5E2-x+-%282k+%2B+2%29=0........plug in highlight%28k=9%29
x%5E2-x+-%282%2A9+%2B+2%29=0
x%5E2-x+-%2818+%2B+2%29=0
x%5E2-x+-20=0

+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2Cx%5E2-x-20%29+

as you can see, -4 is a zero of the polynomial x%5E2-x-20=0