Question 231107
(a+b)^2-(x-y)^2
The difference of any 2 squares, q^2 - r^2, is the sum times the difference.
q^2 - r^2 = (q+r)*(q-r)
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(a+b)^2-(x-y)^2 = {(a+b) + (x-y)}*{(a+b) - (x-y)}
= (a+b+x-y)*(a+b-x+y)
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and 
(2a+b)^2-(x-2y)^2
= {(2a+b) + (x-2y)}*{(2a+b) - (x-2y)}
= (2a+b+x-2y)*(2a+b-x+2y)