Aswimming pool holds 10,000 gallons of water. it is being filled at a rate of 400 gallons per hour.

part a: write an equation for the function modeling the number of gallons of water, y, in the pool x hours after it began to be filled.

part b: what is the rate of change of this function?

We are told that dV/dt=400 gal/hr so that is the rate asked for in part B.

So to find the function for V(t) you need to integrate dV/dt...

V(t)=⌠400 dt

V(t)=400t +C, where C is the initial volume which is not specified so we can assume that C=0, or in terms of y and x for the labels...

y(x)=400x

The second step on the test was the move he was supposed to