Question

Calculus: Help ASAP

Using n = 4 equal-width rectangles, approximate the integral from negative 2 to 2 of the quantity x cubed plus 8, dx. Use the mid-point of each sub-interval to determine the height of each rectangle.

Answer 1

32

Explanation:

To solve this, you need to start by finding the width of the rectangles and the midpoints. If n=4, b=2, a=-2, and the width of each triangle is delta x = b-a / n, then each width is equal to 1 and there will be four midpoints (you can also tell the amount of midpoints by n=4). These midpoints are -1.5, -0.5, 0.5, and 1.5. The height of each of the rectangles is going to be equal to f(x*k), where x*k is the specific mid point. This means that you need to find f(-1.5), f(-0.5), f(0.5), and f(1.5). When putting these into the function you will get 4.625, 7.875, 8.125, and 11.375. Seeing as the Riemann Sum formula says the summation of f(x*k) * delta x, multiply each of the heights by the width of 1 and then add all of the values together. When you do this you will get 4.625 + 7.875 + 8.125 +11.375 which all totals to 32. This means that the approximation of the given integral is 32.

Answer 2

check the picture below.