Question

http://prntscr.com/9mxhx4

Answer 1

I don't know how to explain this without givng it away ...

Answer 2

Well, I'll say this.
Left end riemman sums,
and you know that 2=50/25, and 4=100/25, but you don't get to 100/25 by the left end sum.

Answer 3

Ok, this seems to be not enough, and I understand that. I don't think I as a student would have caught on that.

Answer 4

you are estimating:
\[\Large \int\limits_{a}^{b} f(x)dx \]

** n is the size of each step ... not the number of steps.