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 on x is the tangent line to the curve horizontal?
Under what condition on y is the tangent line to the curve vertical?
can i get some help on how to go about this...thanks