Answer:
V = 91π / 6
Step-by-step explanation:
When we revolve the region about y = 2, we get a cylindrical shape on its side. If we slice the shape into concentric shells, then each shell will have a radius of 2 − y, a thickness of dy, and a length of 7 − x. The volume of the shell is:
dV = 2π r h t
dV = 2π (2 − y) (7 − x) dy
x = 7y², so:
dV = 2π (2 − y) (7 − 7y²) dy
dV = 14π (2 − y) (1 − y²) dy
dV = 14π (2 − 2y² − y + y³) dy
The total volume is the sum of all the shells from y=0 to y=1.
V = ∫ dV
V = ∫₀¹ 14π (2 − 2y² − y + y³) dy
V = 14π (2y − ⅔ y³ − ½ y² + ¼ y⁴) |₀¹
V = 14π (2 − ⅔ − ½ + ¼)
V = 91π / 6
