help with old AP free response

[thebigscott]

Hi, i need to do this for homework but I can't figure it out. If anybody could walk me through the solution that'd be great.

 

(1978 AB 5)

given (xsquared)-xy+(ysquared)=9

 

a. write a general expression for the slope of the curve

 

b. find the coordinates of the points on the curve where the tangents are vertical

 

c. at the point (0,3) find the rate of change in the slope of the curve with respect to x

 

also, if anybody knows a free website with problems and solutions of AP AB calculus free response from the 1970's and 80's please let me know- thanks

[ecoli]

no free web sites. College board doesn't release any more free information then it has to.

[matt grime]

It's called implicit differentiation; google is your friend.