ok so I've got the implicit differentiation down, now i need help on how to find the tangent line...for example...

x^2+y^2- 5x+ 7y= 13

dy/dx = (-2x+5)/(2y+7)

now it asks...

Under what condition onxis the tangent line to the curve horizontal?

Under what condition onyis the tangent line to the curve vertical?

can i get some help on how to go about this...thanks

mathaction