Question

if 1+2+3+......+k=325,find 1 ^3+2^3+3^3+.......k^3​

Answer 1

Answer:

105625

Step-by-step explanation:

so from  given 1st series we will find k

as we know sum of series is n(n+1)/2

we have to find n as sum is 325

so n(n+1)/2=325

we have n=25

then we have k=25

we can now use the formula for cubic sum of series i.e. {n(n+1)/2}^2

={25x26/2}^2

105625 will be the answer

OR

simply square the sum of normal series to find the sum of cubic series