SOLUTION: How do I solve 100x^4=-400x^3+2100x^2 ?

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Question 622284: How do I solve 100x^4=-400x^3+2100x^2 ?
Answer by matineesuxxx(27) About Me  (Show Source):
You can put this solution on YOUR website!
bring everything to one side, factor out an x%5E2 and solve like a normal quadratic.
basically, this is what you do.
100x%5E4%2B400x%5E3-2100x%5E2=0
100x%5E2%28x%5E2%2B4x-21%29=0
100x%5E2%28%28x%5E2%2B7x%29%2B%28-3x-21%29%29=0
100x%5E2%28x%28x%2B7%29-3%28x%2B7%29%29=0 ----> now in this step i noticed that if i factor out an x from the first bracket, and a -3 from the second bracket, then i would end up with an (x+7) as a common factor, so then i could do this:
100x%5E2%28x-3%29%28x%2B7%29=0
therefore X= -7, 0, and 3