Sum and difference of powers
The sum and difference of powers are powerful factoring techniques that, respectively, factor a sum or a difference of certain powers.
Sums of Odd Powers
Differences of Powers
If is a positive integer and and are real numbers,
Note that the number of terms in the long factor is equal to the exponent in the expression being factored.
An amazing thing happens when and differ by , say, . Then and
If we also know that then:
Sum of Cubes
Factorizations of Sums of Powers
Note that all these sums of powers can be factorized as follows:
If we have a difference of powers of degree , then
where are equivalent to respectively.
Note, of course, that some of the signs simply change when we have sum of powers instead of difference. Regardless, observe that the "longer" polynomial in the factorization is simply a binomial theorem expansion of the binomial , except for the fact that the coefficient on each of the terms is . This can be quite useful in problems that might have a sum of powers expression as well as an application of the binomial theorem.
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