Need help 17-20

17. Let f(x) be a function with the derivative given by f'(x) = -x2 + 27 On which of the following intervals is f(x) increasing? a ) (-00 , - 3 ) b ) ( - 00 , 0 ) c ) (0 , 00 ) d) (0,3) e) none 18. A particle moves along the x-axis so that at time t 2 0 its position is given by s(t) = 3t3 - 3t2 - 24t + 80. At what time is the particle at rest? a) t= =only b) t= 3 only c) t= 2 andt= 3 d) t= 2 and t= e) t = 2 only 19. What is the slope of the line tangent to the curve 3x2 - 2y2 = 6x - 2xy at the point (2,3)? a) 0 b) NIW c) 5 d) UIIN e) NIW 20. If f (x) = (x2 + 1)* then f' (x) = a) x(x2 + 1) x-1 b ) 2x2 (x2 + 1) x - 1 c) x In(x2 + 1)x-1 d) In(x + 1) + 2x2 x2+1 e ) ( x 2 + 1 ) * [ In ( x 2 + 1 ) 2x2 x2 +1