Question

14. यदि (1 + 2 + 3 + ... + 10') = 385, तो
(2+4+6+...+20°)का मान क्या होगा?
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Answer 1

Step-by-step explanation:

The formula of 1^2+2^2+3^2+…….n^2=(n×(n+1)×(2n+1))/6

So if n=10 then total sum of squares from 1 to n or 10 will be (10×(10+1)×(2×10+1))/6=(10×11×21)/6=385

So if n=20 total sum of squares from 1 to n or 20 will be (20×(20+1)×(2×20+1))/6=(20×21×41)/6=2870

But given that we have to find sum of squares of number from 2 to 20 here square of 1 is missing so answer will be(sum of squares of number 1 to 20)-(sum of square of 1)=2870–1=2869