i need the problems answered and to show the work thank you

Problem(ll) (5 points) Given a function f (11:) = c, where c is some constant. Show that f'(x) = 0. (Hint: by limit denition.) Problem(12) (5 points) Show that the absolute-value function y = abs($) = |x| is NOT differentiable at x = 0. (Hint: by limit denition.) Problem(l3) (5 points) Show that the absolutevalue function y = t($) = |x 5[ is NOT differentiable at at = 5. (Hint: by limit denition.)