1.

Sum of `n`terms the series : `1^2-2^2+3^2-4^2+5^2-6^2+`A. `-(n(n+1))/(2)`B. `(n(n+1))/(2)`C. `-n(n+1)`D. none of these

Answer» Correct Answer - A
`1^(2)-2^(2)+3^(2)-4^(2)+5^(2)-6^(2)+ . . . . .+(n-1)^(2)-n^(2)`
`=(1-2)(1+2)+(3-4)(3+4)+ . . . . . +(n-1-n)((n-1)+n)`
`=-(1+2+3+4+ . . . .+n)=-(n(n+1))/(2)`


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