7. Express the function $f(x)=\lg \left(x^{2}-x+1\right)$ as the sum of an even function and an odd function, where the odd function is $\qquad$.

Express the function $f(x)=\lg \left(x^{2}-x+1\right)$ as the sum of an even function and an odd function, where the odd function is $\qquad$.
7. $\frac{1}{2} \lg \frac{x^{2}-x+1}{x^{2}+x+1}$ Hint: $f(x)=\frac{f(x)+f(-x)}{2}+\frac{f(x)-f(-x)}{2}$, where, $\frac{f(x)-f(-x)}{2}$ is an odd function.