Question 4623: how do u factor this out..having trouble: x^3 + 8y^3
Found 2 solutions by longjonsilver, rapaljer:
Answer by longjonsilver(2297)   (Show Source):
Answer by rapaljer(4671)  (Show Source):
You can put this solution on YOUR website! Before you begin this problem, you need to recognize the perfect cubes: that is, 1, 8, 27, 64, and 125. In addition to recognizing these perfect cubes, there are two formulas that you will need to factor the difference or sum of cubes.
Notice that these formulas are almost the same, but that they differ only in a couple of signs. Your problem requires the second formula, since it is the sum of cubes. In this formula, you need to decide what is cubed in the first and second position.
The second formula says:
You must write:  in the form of 
Notice that in the formula, the factored form has a binomial times a trinomial. The binomial is pretty easy:  . The answer takes the form like
The trinomial can be formed from the binomial by taking the first and squaring, the middle term is the product of the first times the second, and the third term is the square of the second.
The first sign in the trinomial is always the opposite of the sign in the binomial, and the second sign in the trinomial is always positive. The formula looks like this:
So your answer looks like this:
When simplified it looks like this:
 which is the final answer.
R^2 at SCC
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