<PRE><B>Question 798245</B>
1-xy-20x^2y^2
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Think of 2 numbers whose product is A*C = -20*1 and whose sum is B = -1
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The numbers are -5 and +4
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Substitute -5xy+4xy for -xy to get:
1 -5xy+4xy -20x^2y^2
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Factor the 1st 2 and the last 2 terms separately to get:
= (1-5xy) + 4xy(1-5xy)
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Factor again to get::
= (1-5xy)(1+4xy)
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Cheers,
Stan H.
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