4 6 ( 2. If at point P(a, b) on the graph of y = f(x ), the derivative of the function changes from positive values for x a, then A.x = a is a local maximum B. y = b is a local maximum C.x = a is a local minimum D.y = b is a local minimum 3. The interval where the function y= -4 x + 5 is decreasing is A. (-20, 2)(2. ) B. (-2.2) C. ( -20. 2 3 ) ( 2 5 3 . - ) D. (-2 3.2 3) 4. The function S(x) = = + x has a relative maximum at A X=-4 B. x=2 C. x=-2 D. x=4