`sum_(k=1)^ook(1-1/n)^(k-1)=` a.`n(n-1)` b. `n(n+1)` c. `n^2` d. `(n+1)^2`

Find sum_(k=1)^(n)(1)/(k(k+1)) .

Prove that sum_(k=1)^(n)(1)/(k(k+1))=1-(1)/(n+1).

Prove that sum_(k=1)^n 1/(k(k+1))=1−1/(n+1) .

sum_(n=1)^ootan(theta/(2^n))/(2^(n-1)cos(theta/(2^(n-1))))

The value of sum_(r=1)^n(-1)^(r+1)("^n C r)/(r+1) is equal to a. -1/(n+1) b. 1/n c. 1/(n+1) d. n/(n+1)

If omega is a complex nth root of unity, then sum_(r=1)^n(ar+b)omega^(r-1) is equal to A.. (n(n+1)a)/2 B. (n b)/(1+n) C. (n a)/(omega-1) D. none of these

Find the sum_(k=1)^(oo) sum_(n=1)^(oo)k/(2^(n+k)) .

lim_(n->oo)((n^2-n+1)/(n^2-n-1))^(n(n-1)) is