SOLUTION: How to I factor this problem completely? x^2-18x+81

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Question 622278: How to I factor this problem completely?
x^2-18x+81
Found 2 solutions by solver91311, matineesuxxx:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


Use FOIL in reverse. Hint: -9 times -9 is 81.

John

My calculator said it, I believe it, that settles it
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Answer by matineesuxxx(27) About Me  (Show Source):
You can put this solution on YOUR website!
what two numbers multiply together to give you +81 yet add together to give you -18? the answer is -9. so this equation becomes,
y=%28x%5E2-9x%29%2B%28-9x%2B81%29
well now you can factor out an x from the first bracket and -9 from the second bracket and you will get,
y=x%28x-9%29-9%28x-9%29
now (x-9) is a common factor. so the equation becomes,
y=%28x-9%29%28x-9%29
this is a perfect square, so it is now written as,
y=%28x-9%29%5E2
hope this helps!