Let ƒ : R $ \to $ R be a differentiable function satisfying ƒ'(3) + ƒ'(2) = 0. Then $\mathop {\lim }\limits_{x \to 0} {\left( {{{1 + f(3 + x) - f(3)} \over {1 + f(2 - x) - f(2)}}} \right)^{{1 \over x}}}$ is equal to

Question

Let ƒ : R $ \to $ R be a differentiable function satisfying ƒ'(3) + ƒ'(2) = 0.
Then $\mathop {\lim }\limits_{x \to 0} {\left( {{{1 + f(3 + x) - f(3)} \over {1 + f(2 - x) - f(2)}}} \right)^{{1 \over x}}}$ is equal to