Comment on Activity 3
The key to the calculation is the observation that `b^0=1`. Notice that the expression `b^t` stands for two different things in the equation
`d/(dt)b^t=L(b)b^t`.
On the left, it does not make sense to substitute values of `t` because we are calculating the derivative of the function `b^t`. On the right, we have a formula for that derivative, which is itself a function. It does make sense to substitute a value of `t` — in particular, `t=0` — on the right to find a slope at an individual point.