$\displaystyle x^4 - 9x^2 - y^4 + 9y^2 = -12$

a) Can this curve be represented by a function as y = f(x)?? explain your answer. ----> I know that the answer to this is NO because it doesnt pass the vertical line test so cant be expressed as y=f(x)

b) Can this curve be represented by a function as x = g(y)?? explain your answer. -----> i'm not quite sure what to do about this one.. is the answer to this no also as it doesnt pass the horizontal line test??

help please