Let g(x) be a linear funchion and f(x)= {g(x), x ≤ 0; ((1+x)/(2+x))^(1/x), x>0}, is continuous at x=0. If f^′(1)=f(-1), then the value g(3) is

Let $\displaystyle g(x)$ be a linear funchion and $\displaystyle f(x)=\left\{\begin{array}{cl}g(x) & , x \leq 0 \\ \left(\frac{1+x}{2+x}\right)^{\frac{1}{x}} & , x>0\end{array}\right.$, is continuous at $\displaystyle x=0$. If $\displaystyle f^{\prime}(1)=f(-1)$, then the value $\displaystyle g(3)$ is