Answer:
x =
Step-by-step explanation:
Given a quadratic in standard form, ax² + bx + c : a ≠ 0
Then the axis of symmetry is a vertical line with equation x = h
where h is the x- coordinate of the vertex.
The x- coordinate of the vertex is
= -
f(x) = 5x² - 3x + 5 ← is in standard form
with a = 5 and b = - 3, thus
= -
=
Thus the equation of the axis of symmetry is x =
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