Question

Difficulty: MediumFactoring Polynomials

An engineer needs to simplify a calculation involving the volume of a component, modeled by the polynomial 4y3+12y2−72y4y^3 + 12y^2 - 72y. What is the fully factored equivalent of this polynomial?

  1. 4y(y+6)(y−3)4y(y + 6)(y - 3)Answer
  2. B
    4y(y−6)(y+3)4y(y - 6)(y + 3)
  3. C
    4y(y2+3y−18)4y(y^2 + 3y - 18)
  4. D
    4y(y+6)(y+3)4y(y + 6)(y + 3)

Answer

4y(y+6)(y−3)4y(y + 6)(y - 3)
To fully factor the given expression, first extract the greatest common factor (GCF). All terms share a common factor of 4y4y, yielding 4y(y2+3y−18)4y(y^2 + 3y - 18). Next, factor the resulting quadratic trinomial y2+3y−18y^2 + 3y - 18. The two numbers that multiply to −18-18 and sum to 33 are 66 and −3-3. This gives the binomial factors (y+6)(y + 6) and (y−3)(y - 3). Combining these with the GCF results in the completely factored form 4y(y+6)(y−3)4y(y + 6)(y - 3).

Step-by-Step Solution

1
Identify and extract the greatest common factor (GCF) from all terms in the polynomial 4y3+12y2−72y4y^3 + 12y^2 - 72y.
4y(y2+3y−18)4y(y^2 + 3y - 18)
Factoring out the GCF simplifies the remaining polynomial, making it easier to factor completely.
2
Factor the remaining quadratic trinomial y2+3y−18y^2 + 3y - 18 by finding two integers that multiply to −18-18 and add to 33.
(y+6)(y−3)(y + 6)(y - 3)
The integers 66 and −3-3 satisfy both conditions: 6×(−3)=−186 \times (-3) = -18 and 6+(−3)=36 + (-3) = 3.
3
Combine the GCF with the factored binomials to state the final expression.
4y(y+6)(y−3)4y(y + 6)(y - 3)
This represents the original polynomial decomposed entirely into its lowest degree factors.

Key Concept

Factoring Polynomials with a GCF
Estimated Time:1m 0s
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