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

1-160.

The function is graphed below, along with four left endpoint rectangles which approximate the area from

*to*

*.*

Why does it look like there are only three rectangles?

What happens if the left endpoint is on the

-axis?Since

, the height of the rectangle is. Recall that area under the

-axis is negative, while that above the-axis is positive. Approximateusing these four rectangles.Sum the areas of all four rectangles together. Remember to treat a rectangle's area as negative if it is below the

-axis.