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 Question from Adil: expand the following: (5x-9)(5x+9)

Hi,

This is an exercise with the distributive law which says that for any numbers $a, b$ and $c$, $a(b + c) = ab + ac.$

I an going to illustrate with a different question,

expand $(3x - 5)(2x + 3).$

To use the distributive law I will take $a = 3x - 5, b = 2x \mbox{ and }c = 3.$ with this I get

$(3 x - 5)(2x + 3) = (3x - 5) \times 2x + (3x - 5) \times 3 = 6x^2 -10 x + 9x - 15 = 6x^2 -x - 15.$

Try this with your problem. It simplifies to something simpler than mine.

Penny