The expansions of (x + y)4, (x + y)5, and (x + y)6 are shown below.
(x + y)4 = 1x4 + 4x3y + 6x2y2 + 4xy3 + 1y4
(x + y)5 = 1x5 + 5x4y + 10x3y2 + 10x2y3
+ 5xy4 + 1y5
(x + y)6 = 1x6 + 6x5y + 15x4y2 + 20x3y3 + 15x2y4
+ 6xy5 + 1y6
(a) Explain how the exponent of a binomial is related to the number of terms in its expansion.
(b) How many terms are in the expansion of (x + y)n?