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Q. Evaluate : lim n n + 1 n 2 + 1 2 + n + 2 n 2 + 2 2 + n + 3 n 2 + 3 2 + . . . . . . . . + 1 n

Dear student
limnn+1n2+12+n+2n2+22+n+3n2+32+...+1n=limnn+rn2+r2=limn1n1+rn1n21+r2n2=limnn1+rn1+r2n2Therefore, replacing rn by x and n by dx, we getf(x)=1+x1+x2 and f(x)dx=1+x1+x2dxLower Limit=limnrn=limn1n=0Upper limit=limnrn=limnnn=1Hence the required limit is011+x1+x2dx=tan-1x+12log1+x201=tan-11+12log1+12-tan-10+12log1+02=tan-1tanπ4+12log2-tan-1tan0+12log1=π4+12log2      log1=0
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Dividing numerator and denominator by n2
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