Consider the function

I need to calculate by using the definition of Riemann sum for - right end-points,

so, I started by finding

after that

so, I'm basically asked to provide

as a function of n, without summation symbols, and for this I entered step i) , but it was considered as wrong, so obviously, my mistake is somewhere above,

, here I obtained , but it is actually wrong since all my work-up before is wrong,

can you, please help me with this,

thanks,

dokrbb