- #1
TheRedDevil18
- 408
- 1
Homework Statement
Find the coefficient of x^3 in the binomial expansion of
(2/x - 3x^4)^12
Homework Equations
The Attempt at a Solution
Expanding this out would take too long and I cannot use a calculator to find the coefficient
I know the formula for the expansion
summation (12 choose k) a^k * b^12-k
a = 2/x, b = -3x^4
But how do I find k ?