Question

1² + 2² + 3² + ...... + 10² = 385
than 3² + 6² + 9² ..... + 302 is equal to...?

Answer 1

${1}^{2} + {2}^{2} + {3}^{2} + ...... + {10}^{2} = 385 \\ \\ {3}^{2} + {6}^{2} + {9}^{2} + ..... + {30}^{2} = x \\ 3( {1}^{2} + {2}^{2} + {3}^{2} + .... + {10}^{2}) = x \\ 3 \times 385 = x \\ 1155 = x$