Example

Factoring 10x234x2410x^2 - 34x - 24

Factor 10x234x2410x^2 - 34x - 24 completely by first extracting the GCF and then factoring the resulting trinomial whose leading coefficient is not 1.

Step 1 — Is there a GCF? Yes, the GCF of 10x210x^2, 34x34x, and 2424 is 22. Factor it out:

10x234x24=2(5x217x12)10x^2 - 34x - 24 = 2(5x^2 - 17x - 12)

Step 2 — Classify the expression inside the parentheses. The expression 5x217x125x^2 - 17x - 12 is a trinomial with leading coefficient a=51a = 5 \neq 1. Since the leading coefficient is not 1, use the trial and error or "ac" method to factor it.

Step 3 — Factor the trinomial: Applying the method yields:

2(5x217x12)=2(5x+3)(x4)2(5x^2 - 17x - 12) = 2(5x + 3)(x - 4)

Step 4 — Check.

  • Is the expression factored completely? Yes — neither binomial can be factored further.
  • Verify by multiplying:

2(5x+3)(x4)=2(5x220x+3x12)=2(5x217x12)=10x234x242(5x + 3)(x - 4) = 2(5x^2 - 20x + 3x - 12) = 2(5x^2 - 17x - 12) = 10x^2 - 34x - 24

The completely factored form is 2(5x+3)(x4)2(5x + 3)(x - 4). Unlike examples where extracting the GCF reduces the leading coefficient to 1 (allowing the simpler "undo FOIL" method), this example leaves a trinomial with a1a \neq 1 inside the parentheses, which requires the more involved trial-and-error or "ac" factoring technique. This two-step combination — GCF extraction followed by factoring a trinomial of the form ax2+bx+cax^2 + bx + c with a1a \neq 1 — is a common pattern in the general factoring strategy.

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Updated 2026-04-21

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