The derivative is based upon only those terms containing variables. You take the exponent and make it an integer in front of the variable, with the exponent decreasing by 1.
So x^2 +1 --> 2x, note how the exponent 2 ended up in front of the variable x, and also that the variable is 1 exponent less (^1 instead of ^2). Now if there is already a number in front of the variable, then just multiply it to the exponent: 2x^2 --> 2×2 = 4x
s(t) = -9 - 3t --> the derivative would be -3
because the t^1 decreases to t^0, which equals 1, then 1×-3 = -3
