...is $\displaystyle y'=\frac{-x}{y}$

My book says the second derivative of a circle is also $\displaystyle y''=\frac{-x}{y}$

Every time I do it, I get $\displaystyle y''=\frac{-y}{x}$

So what is the 2nd derivative of a circle?

Por favor show some steps or tell me how you did it?

Ty

Editops! wrong secition. This isn't homework.