Example

Factoring u2−9u+18u^2 - 9u + 18

To factor the trinomial u2−9u+18u^2 - 9u + 18, find two numbers that multiply to 1818 and add to −9-9. Because the constant term (1818) is positive and the middle term (−9u-9u) is negative, both factors must be negative.

List the negative factor pairs of 1818:

  • −1-1 and −18-18: sum is −19-19
  • −2-2 and −9-9: sum is −11-11
  • −3-3 and −6-6: sum is −9-9 The pair −3-3 and −6-6 adds to −9-9.

Use these numbers to write the binomial factors: (u−3)(u−6)(u - 3)(u - 6).

Check the result by multiplying: (u−3)(u−6)=u2−6u−3u+18=u2−9u+18(u - 3)(u - 6) = u^2 - 6u - 3u + 18 = u^2 - 9u + 18.

The factored form is (u−3)(u−6)(u - 3)(u - 6).

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Updated 2026-06-03

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