SOLUTION: I need help factoring this expression: {{{ 21w^4+35w^3-14w^2 }}} Please help.

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Question 777368: I need help factoring this expression:
+21w%5E4%2B35w%5E3-14w%5E2+
Please help.
Answer by FrankM(1040) About Me  (Show Source):
You can put this solution on YOUR website!
+21w%5E4%2B35w%5E3-14w%5E2+ First, factor out 7w%5E2
%287w%5E2%29%283w%5E2%2B5w-2%29
Next we'll have
%283w%2Bx%29%28w%2By%29 where x and y are either 1,-2, -1,2, 2,-1, or -2,1)
So this takes a bit of looking and mental math to figure what's right. We know 3*2 = 6 and 6-1=5 so this is what will work;
%283w-1%29%28w%2B2%29 and the final answer is
%287w%5E2%29%283w-1%29%28w%2B2%29
(You see if we chose 1,-2 the middle term would not be right, it would have been -5w. And the other pairs each would have a different middle term. So only -1,2 worked)