Question

If f(x) = x^3 + 8x² + 11x-20 and x+5 is a factor of f(x), then find all of the zeros of f(x) algebraically

Answer 1

The zeros are (-5,-4,-1)

Explanation:

Since we have a linear factor, we can use the method of long division to get the other factors

What this mean is that we simply divide the polynomial by the linear expression

we have this division result as;

By dividing, we have the other factor as ;

x^2 + 3x - 4

so we simply factorize this

x^2 -x + 4x - 4

x(x-1) + 4(x-1)

(x + 4)(x-1)

So the complete factors are;

(x + 5)(x + 4)(x-1)

To get the zeros, we simply equate each of the terms to zero

and we have our answer as;

-5 , -4 , 1