if `U_n = |[1 , k , k] , [2n , k^2+k+1 , k^2+k] , [2n-1 , k^2 , k^2+k+1]|` and `sum_(k=1->n)U_n=72` then value of `k` is:

If I_(n) = |(1,k,k),(2n,k^(2) + k + 1,k^(2) + k),(2n -1,k^(2) ,k^(2) + k +1)| and sum_(n=1)^(k) I_(n) = 72 , then k =

u_(n) = |{:(1,,k,,k),(2n,,k^(2)+k+1,,k^(2)+k),(2n-1,,k^(2),,k^(2)+k+1):}| and sum_(n=1)^(k) u_(n)=72 then k=

If U_(n) = |[1,K,K],[2n,K^(2)+K+1,K],[2n+1,K^(2)+K+1,K]| and sum_(n=1)^(K)U_(n)=-90 then absolute value of K is equal to

If D_k=|(1, n, n),(2k, n^2+n+1,n^2+n),(2k-1,n^2,n^2+n+1)| and sum_(k=1)^n D_k=56. then n equals

If Delta_k=|(1,n,n), (2k, n^2+n+1, n^2+n), (2k-1, n^2, n^2+n+1)| and sum_(k=1)^n Delta_k = 56, then n is equal to (i)4 (ii)6 (iii)8 (iv)none

D_k=|(1,n,n),(2k,n^2+n+1,n^2+n),(2k-1,n^2,n^2+n+1)| and sum_(k=1)^nD_k=56 then n equals:

If D_k=|(1, n, n),(2k, n^2+n+1,n^2+n),(2k-1,n^2,n^2+n+1)| and sum_(k=1)^n D_k=56. then n equals 4 b. 6 c. 8 d. none of these

If sum_(k=1)^(n)k=210, find the value of sum_(k=1)^(n)k^(2).

If Delta_(k) = |(1,n,n),(2k,n^(2)+n+1,n^(2)+n),(2k-1,n^(2),n^(2)+n+1)|and sum_(k=1)^(n)Delta_(k)=56. then n equals a)4 b)6 c)8 d)None of these

If Delta_(k) = |(k,1,5),(k^(2),2n +1,2n +1),(k^(3),3n^(2),3n +1)|, " then " sum_(k=1)^(n) Delta_(k) is equal to