(p + q)2  = p2 +  2pq + q = 1 represents an equation used in 

1. population genetics  2. Mendelian genetics 
3. biometrics 4. molecular genetics 
(a) (p+q)2=p2+2pq+q2=1, represents an equation used in population genetics lt is a mathematical representation of 'Hardy Weingborg principlc'. Thhis principle says that allele frequncies in a population are stable and is constant from generation to generation, i.e., the gene pool remains a constant.