I'm having some trouble with some of these. It's kinda one of those times where you're doing great in class and then you leave and can't remember anything

1. If a rock is thrown in the air on a small planet with velocity 25 m/s, its height in meters is Y = 25t - 4.9t^2. What is the rock's velocity at t = 3?

2. The slope of the tangent line to the curve Y = 4(sqrt[x]) is _______. The equation for the line is Y = mx + b, where M is ______ and B is ______.