Example

Factoring 18n237n+1518n^2 - 37n + 15

Factor 18n237n+1518n^2 - 37n + 15 completely using the trial and error method. This trinomial has the largest number of first-term factor pairs encountered so far, making the GCF elimination shortcut especially valuable.

Step 1 — Write in descending order. The trinomial 18n237n+1518n^2 - 37n + 15 is already in descending order.

Step 2 — Find factor pairs of the first term. The term 18n218n^2 can be factored into first-degree terms in three ways: n18nn \cdot 18n, 2n9n2n \cdot 9n, or 3n6n3n \cdot 6n.

Step 3 — Find factor pairs of the last term and consider signs. The last term 1515 is positive, so its factors must have the same sign. Since the middle coefficient 37-37 is negative, both factors must be negative: 1-1 and 15-15, or 3-3 and 5-5.

Step 4 — Test all combinations. Three factor pairs for the first term combined with two factor pairs for the last term (each in two possible arrangements) would normally produce many trial factorizations. However, the GCF elimination shortcut removes most of them: since the original trinomial has no common factor, any trial binomial whose terms share a common factor is impossible. For example, (3n3)(6n5)(3n - 3)(6n - 5) is ruled out because 3n3n and 3-3 share a factor of 3. After eliminating invalid combinations, only a few remain to test:

The combination (2n3)(9n5)(2n - 3)(9n - 5) produces 18n210n27n+15=18n237n+1518n^2 - 10n - 27n + 15 = 18n^2 - 37n + 15

Step 5 — Check by multiplying: (2n3)(9n5)=18n210n27n+15=18n237n+15(2n - 3)(9n - 5) = 18n^2 - 10n - 27n + 15 = 18n^2 - 37n + 15

The factored form is (2n3)(9n5)(2n - 3)(9n - 5). With 18n218n^2 having three factor pairs instead of just one or two, the total number of possible trial factorizations grows significantly. This example demonstrates how the GCF elimination shortcut becomes increasingly important as the leading coefficient gains more factor pairs — it eliminates many invalid combinations before any multiplication is needed.

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Updated 2026-04-21

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