Question

Find the coefficient to the x4 term in the expansion of (x + 4) 6.

Answer 1

240

Explanation:

The x^k term will be ...

(6Ck)(x^k)(4^(6-k))

For k=4, this is ...

(6C4)(x^4)(4^2) = 15·16·x^4 = 240x^4

The coefficient of x^4 is 240.

_____

nCk = n!/(k!(n-k)!)