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What are the factors of x2 − 81?

User Hebert
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2 Answers

5 votes
x^2-81
(x+9)(x-9)
x*x=x^2
x*-9= -9x
x*+9= 9x
^^^ These last two cancel each other out
+9*-9 = -81 (neg times pos is neg)
Left with (x^2-81)

I used * as a multiplication sign because an x is confusing when x is your variable
Look up the Box Method- It makes factoring easier!
User Sergio Mcfly PYK
by
8.8k points
4 votes

x^2-81=(x-9)(x+9)
User Pinkey
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7.7k points