Answer:
Step-by-step explanation:
Friends lunch=8+8+8=$32
Blake's lunch=$6
32+6=$40 total
Here are the combinations:
1x18 = 18
18x1 = 18
9x2 = 18
2x9 = 18
6x3 = 18
3x6 = 18
The two parabolas intersect for

and so the base of each solid is the set

The side length of each cross section that coincides with B is equal to the vertical distance between the two parabolas,
. But since -2 ≤ x ≤ 2, this reduces to
.
a. Square cross sections will contribute a volume of

where ∆x is the thickness of the section. Then the volume would be

where we take advantage of symmetry in the first line.
b. For a semicircle, the side length we found earlier corresponds to diameter. Each semicircular cross section will contribute a volume of

We end up with the same integral as before except for the leading constant:

Using the result of part (a), the volume is

c. An equilateral triangle with side length s has area √3/4 s², hence the volume of a given section is

and using the result of part (a) again, the volume is

Perform the indicated multiplication first: -15 + 5q + 4 = 5q - 11
Note that 5q appears on both sides of this equation. Cancelling, we get :
-11 = -11. This is always true. Thus, -5(3-q) +4=5q-11 is true for all q.