SOLUTION: factor 5x2 -8x -4

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Question 691119: factor 5x2 -8x -4
Answer by pmatei(79) About Me  (Show Source):
You can put this solution on YOUR website!
5x%5E2+-+8x-4
ac=%285%29%28-4%29+=+-20
b=-8
Need to find 2 numbers that multiply to -20 and add to -8. Those numbers are -10 and 2. Rewrite -8x as -10x%2B2x
5x%5E2-10x%2B2x-4
Group first 2 terms and the last 2 terms:
%285x%5E2-10x%29+%2B+%282x-4%29
Factor 5x from first parenthesis and 2 from the second one:
5x%28x-2%29+%2B+2%28x-2%29
If you done everything right the 2 parentheses should be the same. In this case %28x-2%29. This is one of the 2 parentheses you are looking for. The second one is formed by the factors written in front of it: ex and 2.

%285x%2B2%29%28x-2%29