SOLUTION: I'm taking intermediate algebra 10 years after I last took it. We've been given a sheet to review factoring and I've been having problems remembering how to factor, particularly t

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Question 223804: I'm taking intermediate algebra 10 years after I last took it. We've been given a sheet to review factoring and I've been having problems remembering how to factor, particularly the rules involving quadratic equations. Here are four of the problems that are giving me grief:
#1. Factor 10x^2+9x-9
I came up with 10xs^2+3(3x-3)
#2. Factor 2ax+2ay-bx-by
My answer is 2a(x+y)-b(x+y)
#3. Factor x(y-8)-7(8-y)
My answer is xy-8x-56-7y
# 4. Factor 4-x^2
Can't even think where to begin with this one!

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
#1. Factor 10x^2+9x-9
I came up with 10x^2+3(3x-3)
= (5x - 3)*(2x + 3)
-------------------
#2. Factor 2ax+2ay-bx-by
My answer is 2a(x+y)-b(x+y)
then combine the terms
= (2a-b)*(x+y)
--------------
#3. Factor x(y-8)-7(8-y)
My answer is xy-8x-56-7y
(8-y) = -(y-8)
= (x+7)*(y-8)
-------------------
# 4. Factor 4-x^2
The difference of 2 squares, a^2 - b^2, is (a-b)*(a+b)
= (2-x)*(2+x)