Question

please answer it fast

Answer 1

answer is
${43}^{2}$
as
${1}^{2} + {2}^{2} + {2}^{2} = {3}^{2} \\ where \: {1 + 2}^{2} = {3}^{2} \\ so \: on \\ last {6}^{2} + {7}^{2} + {..}^{2} = {....}^{2} \\ here {..}^{2} = {42}^{2} \\ and \\ {...}^{2} = {43}^{2}$