A force of 750 pounds compresses a spring 3 inches from its natural length of 15 inches. Find the work done in compressing the spring an additional 3 inches.
They seem to want you to assume a lot. Not really sure why this is even a calc question.
On a force-distance graph, y = 750 when x = 3 and y = 0 when x = 0.
The integral of a force-distance graph gives you force*distance, or work.
So we have
And we want
We know that W(0) is 0, so W(3) must be 2250.