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I'm going through an answer on this site, and I can't see how

$7−2(31−4(7))$ simplifies to $9(7)−2(31)$

What rule is being used here?

source: How to find the inverse modulo m?

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jsan
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1 Answers1

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Notice that $7 - 2(31-4(7)) = 7 - 2*31 + 2*4*7 = 7 + 8*7 - 2*31 = 9(7) - 2(31)$. Just expand the 2 in and simplify.

user77404
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