Explanation:
Tr+1 = nCr * a^(n-r) * b^r.
Therefore the coefficients of the binomial expansion of (p + q)⁶ are 6C0, 6C1, 6C2, 6C3, 6C4, 6C5 and 6C6.
=> 1, 6, 15, 20, 15, 6, 1.
You can also look up Pascal's triangle which gives shortcuts in finding the coefficients for binomial expansions.