Question

Gain a medal!
What are the zeros of the polynomial function: f(x)= x^3− x^2 − 12x?
0, –4, –3
0, –4, 3
0, 4, –3
0, 4, 3

Answer 1

first factor out x

Answer 2

you get x(x^2-x-12)
you can again factor the quadratic equation

Answer 3

sorry, the quadratic expression

Answer 4

@r4ge you know how to factor quadratics?

Answer 5

no I don't :( @lucaz

Answer 6

the quadratic is x^2-x-12
we need two values that add up to -1 (from the -x term) and that when multiplied we get -12 (from the -12 term)

Answer 7

let's try -4 and 3, -4+3=-1, -4*3=-12
they work, so: x^2-x-12 is the same as (x-4)(x+3)

Answer 8

so, the original expression becomes: x(x-4)(x+3), the roots are the values of x that make the function f(x)=0
if we plug in x=0 we will get 0*(0-4)(0+3), this is equal to zero

Answer 9

f(4) = 4*(4-4)*(4+3) = 4*0*(7) = also equal to zero

Answer 10

f(-3) = -3*(-3-4)*(-3+3) = -3*(-7)*0 = zero

Answer 11

the values that make f(x) = 0 are 0, 4 and -3

Answer 12

thank you sososo much!

Answer 13

no problem