Need Help with precalculus problem?

At the surface of the ocean, the water pressure is the same as the air pressure above the water, about 15lb/in2. Below the surface the water pressure increases by about 4.24lb/in2 for every 10 ft of descent.

Write a function f(x) which expresses the water pressure in pounds per square inch as a function of the depth in inches below the ocean surface.


f(x) = 15lb/in2 + [(4.24lb/in2)/120in)x]

15lb/in2 is where the pressure starts at 0 inches below the surface.

Convert 10ft into inches = 120in

It changes 4.24lb/in2 every 120in. Divide by 120 to figure out how much it will change every 1in. Use this number as your slope.

Sorry if this isn't clear, but I hope it helps!


First of all, pounds per square inch is represented as psi, not lb/in^2.

Second of all, f(x) = 4.24x + 15.

Y is pressure in psi, X is every 10 feet of descent.