find the value of 25²+26²+......50²
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use the formula,
Sn = n(n+1)(2n+1)/6
Let S = 25² + 26² + .......+50²
S' = 1² + 2² +.....50² = 50(50+1)(2×50+1)/6
S" = 1² + 2² +....+ 24² =24(24+1)(2×24+1)/6
so,
S = S' - S"
= 50(50+1)(2×50+1)/6 - 24(24+1)(2×24+1)/6
= 228150/6
= 38025
hence, answer is 38025
Sn = n(n+1)(2n+1)/6
Let S = 25² + 26² + .......+50²
S' = 1² + 2² +.....50² = 50(50+1)(2×50+1)/6
S" = 1² + 2² +....+ 24² =24(24+1)(2×24+1)/6
so,
S = S' - S"
= 50(50+1)(2×50+1)/6 - 24(24+1)(2×24+1)/6
= 228150/6
= 38025
hence, answer is 38025
somnathpaul:
will u pls say that how u get 24 ?
qn wants 25² + 26² ....50² ,if we subtract 1²+2²+....24² from 1²+2²+....50²
then we can get
ok
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