### Home > CALC > Chapter 1 > Lesson 1.4.2 > Problem 1-160

1-160.

What happens if the left endpoint is on the *x*-axis?

Since *f*(−1) = 0, the height of the rectangle is 0.

Sum the areas of all four rectangles together. Remember to treat a rectangle's area as negative if it is below the *x*-axis.