Answer:
-4, -2, 4
Step-by-step explanation:
You want the roots of the polynomial x³ +2x² -16x -32.
Factors
The polynomial can be factored by grouping:
x³ +2x² -16x -32
= (x³ +2x²) -(16x +32) . . . . . . group pairs of terms
= x²(x +2) -16(x +2) . . . . . . . . factor each group
= (x² -16)(x +2) . . . . . . . . . . . . factor out the common factor
Now, the difference of squares can be factored:
= (x -4)(x +4)(x +2)
Roots
The zero product rule tells us the roots are the values of x that make the factors zero:
x -4 = 0 ⇒ x = 4
x +4 = 0 ⇒ x = -4
x +2 = 0 ⇒ x = -2
The roots of the polynomial are {-4, -2, 4}.
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Additional comment
The factorization of the difference of squares is a special form:
a² -b² = (a +b)(a -b)
