Here is the expansion of (x + y)n for n = 0, 1,…, 5 :
(x + y)0 = 1
(x + y)1 = x + y
(x + y)2 = x 2 +2xy + y 2
(x + y)3 = x 3 +3x 2 y + 3xy 2 + y 3
(x + y)4 = x 4 +4x 3 y + 6x 2 y 2 +4xy 3 + y 4
(x + y)5 = x 5 +5x 4 y + 10x 3 y 2 +10x 2 y 3 +5xy 4 + y 5
hopefuly this helps you understand
