Question

What is the value of the left Riemann sum approximation to intergal 0 to 50 f(x)dx using the sub intervals [ 0,25] , [25,30] , [30,50] ?

Answer 1

that would be just three rectangles

25f(0) + 5f(25) + 20f(30)

That is,

2
∑ f(x_k) ∆x_k
k=0