400
A person is biking down a road and the function P(x) gives their position. Note, P(x) is not linear. P(5)=32 ft and P'(5)=4 ft/sec. Why is P(6)=36ft an estimate instead of an exact answer?
What is the slope of P(x) is not constant and therefore is always changing so although the P'(5)=4, P'(5.5)=??. P'(5.5) (or any other x between 5 and 6) could be bigger or smaller than 4 and thus the biker would likely not be at exactly 36ft at 6 seconds.