5) A ladder 25 feet long is leaning against the wall of a house. The base of the ladder is pulled away from the wall at a rate of 2 feet per second. How fast is the top of the ladder moving down the wall when its base is 7 feet from the wall? 6) Use the implicit differentiation to find y' : a)x' +y* =x2 -sin x b) 5x2 + x tany = xy