Example

Factoring 5x3+15x220x5x^3 + 15x^2 - 20x

To factor the polynomial 5x3+15x220x5x^3 + 15x^2 - 20x completely, start by checking for a greatest common factor (GCF).

Step 1 — Identify the GCF of the three terms. The GCF of 5x35x^3, 15x215x^2, and 20x-20x is 5x5x.

Step 2 — Factor out 5x5x from the polynomial: 5x(x2+3x4)5x(x^2 + 3x - 4). The expression inside the parentheses is now a trinomial with a leading coefficient of 11.

Step 3 — Factor the trinomial x2+3x4x^2 + 3x - 4 by finding two numbers that multiply to 4-4 and add to 33. The numbers 1-1 and 44 satisfy both conditions because 14=4-1 \cdot 4 = -4 and 1+4=3-1 + 4 = 3.

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

Step 5 — Verify by multiplying: 5x(x1)(x+4)=5x(x2+4xx4)=5x(x2+3x4)=5x3+15x220x5x(x - 1)(x + 4) = 5x(x^2 + 4x - x - 4) = 5x(x^2 + 3x - 4) = 5x^3 + 15x^2 - 20x ✓.

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

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Updated 2026-04-29

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