SOLUTION: Tutors I have the following problem: Use substitution to determine that -4,2,1are zeros of f(x)=x^3+3x^2-4x Thank you

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Tutors I have the following problem: Use substitution to determine that -4,2,1are zeros of f(x)=x^3+3x^2-4x Thank you      Log On


   

Question 141581: Tutors I have the following problem: Use substitution to determine that -4,2,1are zeros of f(x)=x^3+3x^2-4x
Thank you
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
f%28x%29=x%5E3%2B3x%5E2-4x
f%28-4%29=%28-4%29%5E3%2B3%28-4%29%5E2-4%28-4%29
f%28-4%29=-64%2B48%2B16
f%28-4%29=0
x=-4 is a zero of f(x).
f%282%29=2%5E3%2B3%282%29%5E2-4%282%29
f%282%29=8%2B12-8
f%282%29=12
x=2 is not a zero of f(x).
f%281%29=1%5E3%2B3%281%29%5E2-4%281%29
f%281%29=1%2B3-4
f%281%29=0
x=1 is a zero of f(x).