Solve for x. Can someone explain

Which equation can be simplified to find the inverse of y = 2x2?

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =

The serenity and the mystic are sail boats. the serenity and the mystic start at the same point and travel away from each other in opposite directions. the serenity travels at 16 mph and the mystic travels at 19 mph. how far apart will they be in 3 hours?