Set up the Riemann sum of f(x)=x^2-2 by partitioning the interval [1,5] into equal subintervals and use the left endpoint of each subinterval for x.

I know the riemann sum in it's general form is

n

Σ f(ci)delta-xi and delta-x = (b-a)/n

i=1

But I have trouble with figuring out the subintervals and using the left endpoint. How do I come up with the left endpoint Ci?