Use a simple area formula from geometry to find the area under function A(x) that gives the area under the function f(x) = 9 on the interval [2, x].

Answer 1

width * height = (x-2)*9 = 9x - 18

Answer 2

use simple area formula from geometry to find the area function A(x).Confirm that A'(x)=f(x) where f(x)=3x-3. ;. [a,x]=[2,x]