1-18 Find the volume of the solid obtained by rotating the region bounded by the given curves about the specified line. Sketch the region, the solid, and a typical disk or washer. 1. y=2x, y = 0, x = 1, x = 2; about the x-axis 2. y = 1 x, y = 0; about the x-axis 3. y = 1/x, x = 1, x = 2, y = 0; about the x-axis 7. y=x, y=x, x=0; about the x-axis 8. y=x, y=5-x; about the x-axis == 9. y = x, x = 2y; about the y-axis