Explain what it mean when elimination results in a equation that is always true

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 bottom of a vase is a square.each side measury y+11 units.the square has a perimeter of 55 units what is the value of y?

Sections of prefabricated wood are each 5 1/3 feet long. how long are 7 1/2 sections placed end to end?