If you'd graph this function, you'd see that it's positive on [-1.5,0], and that it's possible to inscribe 3 rectangles on the intervals [-1.5,-1), (-1,-0.5), (-0.5, 1].
The width of each rect. is 1/2.
The heights of the 3 inscribed rect. are {-2.25+6, -1+6, -.25+6} = {3.75,5,5.75}.
The areas of these 3 inscribed rect. are (1/2)*{3.75,5,5.75}, which come out to:
{1.875, 2.5, 2.875}
Add these three areas together; you sum will represent the approx. area under the given curve on the given interval: 1.875+2.5+2.875 = ?
The reason is because it is not just 6 it is - 6 so when there are two negative numbers they don't subtract they add if it was 6n then it was to be subtracted
