Question 19 Find the third derivative of f(x) = O f'(x)= - 1 36x - - 7sinx 16 f'(x)= +7sinx x5 1 f'(x)= +7sinx 36x f'(x) = - 16 - 7sinx x5 - 2 3x +7cosx. Question 20 Find the derivative of y = 12x+ y' = 48x-35 + 6 +8cscxcotx Oy' = 48x-35 y'=48x3 8 +8cscxcotx x Oy' =48x-35 8 -8cscxcotx X 5 O y'=48x- +8cscxcotx 7x6 4 5 -8cscx. x7 Question 21 Use the limit definition of the derivative to find f'(x) when f(x) = -6x. O f'(x)=-12x O f'(x)=2x O f'(x)=12x-6h O f'(x)=12x Question 25 Find the linear approximation of f(x) = 5x when x = -1. L(x) = -1+ (x+1) O O L(x)=-1- 1-1(x+1) O L(x)=-1++ (x-1) O L(x)=-1-(x-1)