how do i find the finite approximation to estimate the area using the lower sum of 4 rectangles for f (x) = 4-x^2 between x=-2 and x=2?

... ?

The primary rectangle would be from - 2 to - 1.

f ( - 2) = 0

f ( - 1) = 2

this rectangle has 0 stature, subsequently it has no territory. A = length * width = 0.

second rectangle from - 1 to 0

f ( - 1) = 2

f (0) = 4

this rectangle has stature of 2 (the base). range = stature * width = 2 * 1 = 2

third rectangle from 0 to 1 is the same

A3 = 2

fourth rectangle from 1 to 2 is the same as the first:

A4 = 0 * 1 = 0

Add up to range = A1 + A2 + A3 + A4 = 4