Janna
secondary
student

Hi! I was just wondering how you would factor x2 - 9y2.

Thanks!

Hi Janna,

To be able to factoring you need to know a few basic facts and then recognize some patterns. For your problem the fact is the difference of squares formula,

a2 - b2 = (a - b)(a + b) You can verify that this is true by expanding the right side.

The "pattern recognition" part is seeing x2 - 9y2 as a difference of squares. That is you need to see

x2 - 9y2 as x2 - (3y)2 and use the difference of squares formula with a = x and b = 3y

Cheers,
Harley
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