If $\displaystyle A$ is a square matrix and $\displaystyle x^TAy=(Ax)^Ty$ for all $\displaystyle x,y\in R^n$, then prove $\displaystyle A$ is a symmetric matrix. ie. prove $\displaystyle A^T=A$

I cant just go $\displaystyle x^TAy=x^TA^Ty$ rite? So what should i do instead?