Question

What are the zeros of the polynomial function f(x)=x^3-2x^2-8x?

Answer 1

Answer: -2, 0, 4

Set the equation equal to zero.

x³ - 2x² - 8x = 0

Factor out x in the equation, since all the terms (x³, -2x², and -8x) are divisible by x. You can check your accuracy using the Distributive Property.

x(x² - 2x - 8) = 0

Factor out the polynomial. To do this, find two numbers that multiply to get the last term, -8, and add together to get the middle term, -2. In this case, those two numbers are -4 and 2 (-4 × 2 = -8 and -4 + 2 = -2). Don't forget about the x that was factored out before!

x(x - 4)(x + 2) = 0

Set each factor equal to zero and solve for x. The factors in the equation are x, (x - 4), and (x + 2).

• x = 0
• (x - 4) = 0

        x = 4

• (x + 2) = 0  

        x = -2

The zeros of the polynomial function are -2, 0, and 4.