division & rational zeros?

Question

divide!
1. X + 4 into X^3 - 28X - 48


List all possible rational zeros. then find all the zero of the function.

1. f(x) = x^3 + x^2 - 10x + 8

2. f(x) = x^3 + 2x^2 - 11x - 12

Answer 1

1.

f(x) = x^3 + x^2 - 10x + 8
Possible rational zeros are the factors of 8; that is, they are
± 1, ± 2, ± 4, ± 8

To find the zeros, test each rational zero and determine if we get f(x) = 0.

f(1) = 1 + 1 - 10 + 8 = 0.
Since 1 is a zero, (x - 1) is a factor. Use long division to get the remaining two zeros.

2) f(x) = x^3 + 2x^2 - 11x - 12

Possible rational zeros:
± 1, ± 2, ± 3, ± 4, ± 6, ± 12

Do the same step for above.