Find a mathematical model for the verbal statement.
1. A varies directly as the square of r.
2. V varies directly as the cube of l.
3. Y varies inversely as the square of x.
4. H varies inversely as the square root of s.
5. F varies directly as g and inversely as r2.
6. Z varies jointly as the square of x and the cube of y.
7. The rate of change R of the temperature of an object is directly proportional to the difference between the temperature T of the object and the temperature Te of the environment.
8. For a constant temperature, the pressure P of a gas is inversely proportional to the volume V of the gas.
9. The electric power P of a direct current circuit is jointly proportional to the voltage V and the electric current I.
10. The gravitational attraction F between two objects of masses m1 and m2 is jointly proportional to the masses and inversely proportional to the square of the distance r between the objects.