12. [-/3 Points] DETAILS LARCALC11 7.3.031. MY NOTES ASK YOUR TEACHER Use the disk method or the shell method to find the volumes of the solids generated by revolving the region bounded by the graphs of the equations about the given lines. x1/2 + y1/2 = a1/2 X = 0 y = 0 (a) the x-axis (b) the y-axis (c) the line x = aJse the method of cylindrical shells to find the volume of the solid generated by revolving the region bounded by the graphs of the equations and/or inequalities about the indicated axis. y = x2 + 4x, y = 0; the yaxis Sketch the region and a representative rectangle