Example

Factoring 4x3+16x220x4x^3 + 16x^2 - 20x

To factor the polynomial 4x3+16x220x4x^3 + 16x^2 - 20x completely, always check for a greatest common factor (GCF) first.

Step 1 — Identify the GCF of the three terms. The GCF of 4x34x^3, 16x216x^2, and 20x-20x is 4x4x.

Step 2 — Factor out the GCF from the polynomial: 4x(x2+4x5)4x(x^2 + 4x - 5). Notice that after factoring the GCF, the remaining trinomial has a leading coefficient of 11.

Step 3 — Factor the trinomial x2+4x5x^2 + 4x - 5 by finding two numbers that multiply to 5-5 and add to 44. The factors of 5-5 are 1-1 and 55, and their sum is 1+5=4-1 + 5 = 4.

Step 4 — Use these numbers to write the binomial factors: (x1)(x+5)(x - 1)(x + 5). Combine this with the GCF to write the complete factorization: 4x(x1)(x+5)4x(x - 1)(x + 5).

Step 5 — Check the result by multiplying: 4x(x1)(x+5)=4x(x2+5xx5)=4x(x2+4x5)=4x3+16x220x4x(x - 1)(x + 5) = 4x(x^2 + 5x - x - 5) = 4x(x^2 + 4x - 5) = 4x^3 + 16x^2 - 20x ✓.

The completely factored form is 4x(x1)(x+5)4x(x - 1)(x + 5).

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Updated 2026-04-29

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