4. Find values of x, if any, at which f is not continuous. (a) f (x) = > (x-1) x2-1 (b) f (x ) = (2x+1) 4x2+4x+5 2x +3, x54 (c) f (x ) = 17+- 16 , x>4 (d) f (x) = (x+2) (x2+4) 5. Find the value of the constant k, if possible, that will make the function continuous everywhere. (9-x2, x2-3 (a) f(x) = K 12. X 2