SOLUTION: 3x^4-81xy^3 i need help on how to work it out

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Question 348704: 3x^4-81xy^3 i need help on how to work it out
Found 2 solutions by ewatrrr, vleith:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
Hi,
If I am understanding your question properly, the idea is to simplify by factoring out what each term has in common. In this case both terms have 3*x in common:
3%2Ax%5E4-81%2Ax%2Ay%5E3
.
3x%28x%5E3-27%2Ay%5E3%29

Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
3x%5E4-81xy%5E3
3x%2A+%28x%5E3+-+27y%5E3%29 The terms on the right are a difference of 2 cubes
Use this formula to solve
http://www.purplemath.com/modules/specfact2.htm
Here is the solution
http://www.wolframalpha.com/input/?i=3x^4-81xy^3