\(\eqalign{
& S = {2^2} + {4^2} + {6^2} + ... + {20^2} \cr
& S = {\left( {2.1} \right)^2} + {\left( {2.2} \right)^2} + {\left( {2.3} \right)^2} + ... + {\left( {2.10} \right)^2} \cr
& S = {2^2}{.1^2} + {2^2}{.2^2} + {2^2}{.3^2} + ... + {2^2}{.10^2} \cr
& S = {2^2}.\left( {{1^2} + {2^2} + {3^2} + ... + {{10}^2}} \right) \cr
& S = {2^2}.385 = 4.385 = 1540 \cr} \)
