The first and last terms of the expansion of (a + x)7 are a7 and x7 respectively. The powers of ‘a’decrease and the powers of ‘x’ increase moving from left to right. Hence
(a + x)7 = a7 + 7a6x + 21a5x2 + 35a4x3 + 35a3x4 + 21a2x5 + 7ax6 + x7
Problem 2. Determine, using Pascal’s triangle method, the expansion of (2p − 3q)5.