+121 What's the coefficient of the $x2y4$ term in the expansion of (x+y)6?
+613 We can expand (x + y)^6 as (x + y)(x + y)(x + y)(x + y)(x + y)(x + y).
When we expand (x + y)(x + y)(x + y)(x + y)(x + y)(x + y), we find that there are 10 terms that are equal x^2*y^4.
So the coefficient of x^2*y^4 is 10.
