# Write an equation that expresses the following relationship. y varies directly as x and inversely as the square of z.

We will use the concept of direct proportion and indirect proportion to write the required equation.

## Answer : Equation y = (k x / z^{2}) expresses the relationship, y varies directly as x and inversely as the square of z

Let's see that how we will use the concept of direct and indirect proportion to write the required equation.

**Explanation :**

It is given that y varies directly as x and inversely as the square of z.

So, directly proportional means that when x increases y should increase, and when x decreases y should also decrease in the same ratio

Hence we can write, y =** **x ........... ( 1)

Also indirectly proportional that when z increases then y should decrease and when z decreases then y should increase. Here it is given that y is inversely proportional to the square of z.

Hence, y = 1/z^{2 }........... (2)

On combining equation 1 and 2 we get,

y = x / z^{2}

A constant k comes on the removal of the proportionality sign

Therefore required equation = kx / z^{2 }