6. Find f'(x) 1 ex y = 727. Find f '(x) sin (xy) = x2 - y 8. Find f'(x) y = (cos x)x9. A balloon is rising at a constant speed of 5 ft/s. A boy is cycling along a straight road at a speed of 15 ft/s. When he passes under the balloon, it is 45 ft above him. How fast is the distance between the boy and the balloon increasing 3 s later? (related rates) 10. L'Hopitals Rule Evaluate the limit 2x 2x 1_ e 6' 36 1n(x+1)