Question

10^2+12^2+14^2+......+26^2=??

Answer 1

Answer:

3156

Step-by-step explanation:

• Used formula:
• (1² + 2² + 3² + ... + n²) =1/6*n(n + 1)(2n + 1)

--------

• 10²+12²+14²+......+26² =
• (2*5)²+(2*6)² + (2*7)² + ... + (2*13)² =
• 4*(5²+6²+7²+...+13²) =
• 4*(1²+2²+...+13² - (1²+2²+3²+4²)) =
• 4*(1/6*13(13+1)(2*13+1) - (1+4+9+16)) =
• 4*(1/6*13*14*27- 30) =
• 4*(819 - 30) =
• 4*789 =
• 3156