Question

Compute the value of the integral using geometry.

integral from -4 to 1 of (2x +8)dx

Answer 1

first graph y = 2x + 8,,
now, using the boundaries given,
find the value of y at x = -4, and
find the value of y at x = 1:
at x=-4, y = 2(-4) + 8 = 0
at x=1, y = 2(1) + 8 = 10
now, look for these points on your graph and draw a vertical line (this is only a guide) from this point to x-axis.
what figure do you obtain?
from that, find the area using the figure you obtained, (dimensions can be readily calculated by coordinates given)

hope this helps. :)