Show that volume of the solid generated by revolving y=1/x between x=1,2x=infinity about x-axis

Answer 1

by x=1,2 do you mean 1.2 or 6/5?

Anyway, the volume from x=a to ∞ is

∫[a,∞] πy^2 dx
= ∫[a,∞] π/x^2 dx = π/a