I'm struggling in the process of the questions 15; I attached the answer of these questions in the last image as the book provided. Please help me, thank you so much!

Section 7.2 1. T 3. Recall that "dx" does not just "sit there;" it is multiplied by A(x) and represents the thickness of a small slice of the solid. Therefore dx has units of in, giving A(x) dx the units of in3. 5. 48TV/3 /5 units 3 7. 12 / 4 units 3 9. 97 / 2 units 3 11. 12 - 27 units3 13. (a) 7 / 2 (b) 57/6 (C) 47 /5 (d) 87 / 15 15. (a) 47 /3 (b) 271 / 3 (c) 47/3 (d) 7 / 3 17. (a) 72/2 (b) 12/2 - 4TT sinh -1(1) (c) 72/2 + 4 7 sinh -1(1)In Exercises 13 - 18, a region of the Cartesian plane is de- scribed. Use the Disk/Washer Method to find the volume of the solid of revolution formed by rotating the region about each of the given axes. 13. Region bounded by: y = vx, y = 0 and x = 1. 20 Rotate about: (a) the x-axis (c) the y-axis (b) y = 1 (d) x = 1 14. Region bounded by: y = 4 - x2 and y = 0. Rotate about: (a) the x-axis (c) y = -1 21 (b) y = 4 (d) x =2 15. The triangle with vertices (1, 1), (1, 2) and (2, 1). Rotate about: (a) the x-axis (c) the y-axis (b) y = 2 (d) x =1 22 16. Region bounded by y - x2 - 2x + 2 and y = 2x - 1. Rotate about: (a) the x-axis (c) y = 5 (b) y = 1 17, Region bounded by y = 1/Vx2 + 1, x = -1, x = 1 and the x-axis. Rotate about: (a) the x-axis (c) y =-1 (b) y = 1