Thanks, works perfectly for #6 where the function is simple [2y,2x] and the slope was simply 3t.

I tried the exact same procedure on #7. however the function is now [8(4x+9),18(4x+9y)] and the slope is -1/6 from points (-9,4) to (3,2). I wonder if the variable bounds are [-9,3]? The book gives a solution of 400.

Ans: Correct on the bounds. Recall the param. uses y-y1=-1/6*(x-x1) , using 3,2 we have y-2=-1/6*(x-3) , solving for y and using t yields:

y=-1/6t + 5/2 . ok?

Now let t run from -9 to 3 and you got it!

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