Question

If 1^3+^2^3+3^3...= 8281, then find 1+2+3+.....+k​

Answer 1

Answer:91

Step-by-step explanation:sum of cube of first n term is (n(n+1))^2/4. And sum of first n term is (n(n+1))/2.

In question sum of cube of n term is given by which we can find the sum of first n term which is √8281=91

Answer 2

Answer:

91

Step-by-step explanation:

1³+2³+3³.....k³ = [k(k+1)/2]2

8281 =[ (k(k+1))/2]²

k(k+1)/2 = 91

k²+k - 182 = 0

(k+14)(k-13) = 0

k = 13 (accepted value)

k = -14(rejected value)

1+2+3+.....k = k(k+1)/2 = (13×14)/2 = 91