Use this equation to approximate the internal temperature of the potato at time t equals three. So what are we going to do? Well, we're going to think about what's going on at time t equals zero, right over here. We want the equation of the tangent line, which might look something like this, at t equals zero. So this thing would be of the form y is equal to the slope of the equation of the tangent line. Well, it would be the derivative of our function at that point, so dh dt, times t, plus our y-intercept. Where does it intersect the y-axis here?