I have three questions and I have no idea how to solve them. Compare dy and delta y for y=-4x^2+4 at x=2 with delta x=dx=-0. Give your answers to...

I have three questions and I have no idea how to solve them.

1. Compare dy and delta y for y=-4x^2+4 at x=2 with delta x=dx=-0.04. Give your answers to four decimal places.
2. The measurement of the radius of the end of a log is found to be 26 inches, with a possible error of 1/2 inch. Use differentials to approximate the possible propagated error in computing the area of the end of the log.
3. Find the equation of the tangent line T to the graph of f(x)=5sinx at the given point (9, 5sin9).