Summation

Please explain how to solve such questions.
Answer to this question is
\((n²(n+1)²(2n+1)/12\)

@RithvikSubash said in Summation:
Please explain how to solve such questions.
Answer to this question is
\((n²(n+1)²(2n+1)/12\)I am not able to understand how to use the inequality
1≤i,j≤n
While solving the problem

@RithvikSubash It means both i and j lies between [1,n]
first put i=1, then open the summation in j squared , put i = 2 and then again open the summation for j squared and so on till i=n. then add all the summations.