# lost again

• Nov 11th 2007, 10:38 AM
lkrb
lost again
Give a formula for the coefficient of x^k in the expansion of (x^2 - 1/x)^100, where k is an integer. ( x^8 means x to the power of 8, ^ means to the power of).
• Nov 11th 2007, 12:36 PM
topsquark
Quote:

Originally Posted by lkrb
Give a formula for the coefficient of x^k in the expansion of (x^2 - 1/x)^100, where k is an integer. ( x^8 means x to the power of 8, ^ means to the power of).

Use the binomial theorem:
$(a + b)^n = \sum_{k = 0}^n {n \choose k} a^{n-k}b^k$

So here we have $a = x^2$ and $b = \frac{1}{x}$. You do the rest.

-Dan