What is the coefficient of the term x7y in the expansion of (x + y) 8?

We have to find the coefficient of the term x^7 y in the expansion of: (x + y) ^8a = x, b = y, n = 8And the expansion is: n n

∑ () a ^ (n-k) b ^k

k=0 ka^ (n-k) b^k = x^7 ySo : k = 1nCk = 8C1 = 8Answer: The coefficient of the term x^7y is 8.