I have answered the following questions. Please help me check to see if they are correct. If they are not correct, please explain why. Thank you :)

Question 11 of 20 > Let y = x sin x. Then y" is O -2 sin x - x COS X O 2 sin x + x cos x 2 cos x - x sin x 2 sin x - X COS X 2 cos x + x sin xQuestion 12 of 20 > The instantaneous rate of change of f(x) = vx + 5 at c = 9 is al- OOOOO\fQuestion 16 of 20 > Let f(x} = x + 2' . Then which of the following is the largest interval, of those listed, for which f'(x) Let f(x) = sin x - x. if x E [0, 2x], then f has a horizontal tangent line for each x in O (0, 2x} O (2 x}Question 18 of 20 > The derivative of f(x) = vx - 4 at x = 4 is N/- Al- N/- OOOOO