Troy was trying to catch up with the rest of his group, who had left earlier on a kayaking trip. Troy paddled 8 hours
downstream, covering 72 miles before realizing that he had passed his group's campground. He had to paddle back
upstream for 18 miles to get back to his group's campground. If the trip back upstream took Troy 6 hours, how fast
was the river flowing (in mph)?
A. 2 mph
B. 3 mph
C. 6 mph
D. 9 mph

To find the extreme values of a function f(x. y) on a curve x-x(t), y y(t), treat f as a function of the single variable t and use the chain rule to find where df/dt is zero. in any other single-variable case, the extreme values of f are then found among the values at the critical points (points where df/dt is zero or fails to exist), and endpoints of the parameter domain. find the absolute maximum and minimum values of the following function on the given curves. use the parametric equations x=2cos t, y 2 sin t functions: curves: i) the semicircle x4,y20 i) the quarter circle x2+y-4, x20, y20 b, g(x, y)=xy