Find the volume of the solid

Question

Using disks or washers, find the volume of the solid obtained by rotating the region bounded by the curves y=x² and y=4 about the line y=4

Answer 1

x² = 4; x = ±2; volume v = π∫_-2²(4 - x²)²dx = 2π(16x - 8x³/3 + x⁵/5)₀² = 2π(32 - 64/3 + 32/5) = 512π/15