Jack is performing an experiment in a laboratory. The resulting rise in temperature, t(x), of the chemical under observation, over time x, in hours, for the first ten hours can be modeled by a cubic function. Each of the following functions is a different form of the cubic model for the situation given above. Which form would be most helpful if attempting to determine the time at which the temperature is approximately constant?


t(x) = 0.05x(x2 - 15x + 75) + 43.75

t(x) = 0.05(x - 5)3 + 50

t(x) = 0.05(x3 - 15x2 + 75x + 875)

t(x) = 0.05x3 - 0.75x2 + 3.75x + 43.75