SOLUTION: When factored completely, how is 7x^2-21xy-28y^2 written? I need help with this problem because I know how to solve it by looking at it but I need to show work.
Question 960756: When factored completely, how is 7x^2-21xy-28y^2 written? I need help with this problem because I know how to solve it by looking at it but I need to show work. Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! 7x^2 -21xy -28y^2
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the coefficient of x^2 is 7 which is a prime number, therefore we have
(7x +or- ?) * (x +or- ?)
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now we factor 28 (coefficient of y^2)
1 * 28
2 * 14
4 * 7
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we want a -21 (coefficient of xy), therefore
(7x + 7) * (x - 4) gives us the desired results
