Find the variation constant and an equation of variation where y varies inversely as x and y=11 when x=2.

2)Find an equation of variation where y varies inversely as the square of x, and where y=0.40 when x=0.1.

3)find an equation of variation in which y varies jointly as x and z, and y=8 when x=4 and z=2.

4)Find an equation of variation where y varies jointly as x and the square of z, and where y=165 when x=77 and z=5.