How to Factor Trinomials by Finding the Greatest Common Factor

To factor trinomials, you can either find the greatest common factor or unFOIL. You factor trinomials by finding the GCF if a common factor is available.

Factoring trinomials is a matter of recognizing what you have so you know which method to apply. Follow these guidelines when factoring trinomials:

  • Find the GCF if a common factor is available.

  • Use unFOIL if the trinomial is of the form ax2 + bx + c.

  • After checking for both the right form for unFOILing and the GCF, you might find that neither fits. If so, then you’re done! The trinomial can’t be factored.

Factor this expression by finding the GCF:

12x2y4 + 16xy3 – 20x3y2
  1. Determine any common numerical factors.

    Each term has a coefficient that is divisible by a power of 2, which is 4.

  2. Determine any common variable factors.

    Each term has x and y factors. The prime factorizations should help to show what the GCF is.

  3. Write the prime factorizations of each term.

    12x2y4 = 22 × 3 × x2y4

    16xy3 = 24 × xy3

    –20x3y2 = – 22 × 5 × x3y2

    The GCF is the product of all the factors that all three terms have in common.

  4. Find the GCF.

    The GCF contains the lowest power of each variable and number that occurs in any of the terms. Each variable in the sample problem has a factor of 2.

    If the lowest power of 2 that shows in any of the factors is 22, then 22 is part of the GCF.

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