Please help with only 3, 5, 19, and 21 (I do not understand how to do this)

3. (a) From the given graph of f, state the numbers at which f is discontinuous and explain why. (b) For each of the numbers stated in part (a), determine whether f is continuous from the right, or from the left, or neither. VA -4 -2 4 6 .X19-24 Explain why the function is discontinuous at the given number a. Sketch the graph of the function. 19. f (x) = 0 =-2 x +2x+3 ifx=-1 21. f(x) = 7= -1 if x > - 15-6 The graph of a function f is given. (a) At what numbers a does lim -. f(x) not exist? (b) At what numbers a is f not continuous? (c) At what numbers a does lim .-a f(x) exist but f is not continuous at a? 5. VA 6. VA O