Example

Factoring 8x2y98y8x^2y - 98y

Factor 8x2y98y8x^2y - 98y completely by first extracting a GCF that includes a variable, then applying the difference of squares pattern to the remaining binomial.

Step 1 — Is there a GCF? Yes. The two terms 8x2y8x^2y and 98y98y share a numerical factor of 22 and a variable factor of yy. The GCF is 2y2y. Factor it out:

8x2y98y=2y(4x249)8x^2y - 98y = 2y(4x^2 - 49)

Step 2 — Is the binomial a difference of squares? Yes: 4x2=(2x)24x^2 = (2x)^2 and 49=7249 = 7^2, so 4x249=(2x)2724x^2 - 49 = (2x)^2 - 7^2.

Step 3 — Factor as a product of conjugates. Apply the pattern with a=2xa = 2x and b=7b = 7:

2y((2x)272)=2y(2x7)(2x+7)2y((2x)^2 - 7^2) = 2y(2x - 7)(2x + 7)

Step 4 — Check by multiplying:

2y(2x7)(2x+7)=2y(4x249)=8x2y98y2y(2x - 7)(2x + 7) = 2y(4x^2 - 49) = 8x^2y - 98y

The completely factored form is 2y(2x7)(2x+7)2y(2x - 7)(2x + 7). This example illustrates how a common factor — here 2y2y, which includes a variable — can disguise a difference of squares. Neither 8x2y8x^2y nor 98y98y appears to be a perfect square on its own; only after extracting the GCF of 2y2y does the recognizable structure (2x)272(2x)^2 - 7^2 emerge inside the parentheses. Always look for a common factor first, because it may reveal a special product pattern that would otherwise remain hidden.

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Updated 2026-04-21

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