Thursday, December 19, 2013

There are a few ways to remember how to factor the sum and difference of cubes.  First, remember all the perfect cubes from 1 to 10. Those cubes are as follows

1, 8, 27, 64, 125, 216, 343, 512, 729, 1000

The formulas for factoring sum and difference of cubes are as follows:

a^3+ b^3 = (a+b)(a^2 - ab + b^2)

a^3 - b^3 = (a-b)(a^2 + ab + b^2)

You can remember the terms by thinking of a and b in the first set of parentheses then squaring a, multiplying a and b and squaring b. The signs between terms for sum of cubes is same, negative, positive and for difference of cubes it's negative, positive, positive.

You can remember the signs another way.. Same, Opposite, Always Positive.  If you remember the word SOAP it will help you get the correct signs when factoring.

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