Question
If $\text{f}:[-5,\ 5]\rightarrow\ \text{R}$ is a differentiable function and if f'(x) does not vanish anywhere, then prove that $\text{f}(-5)\neq\text{f}(5).$

Answer

For, Rolle’s theorem, if
f is continuous is [a, b]
f is derivable in [a, b]
f(a) = f(b)
Then, $\text{f}'\text{(c)}=0,\ \text{c}\in(\text{a},\ \text{b)}$
It is given that f is continuous and derivable, but $\text{f}'\text{(c)}\neq0$
$\Rightarrow\ \text{f(a)}\neq\text{f(b)}$
$\Rightarrow\ \text{f}(-5)\neq\text{f}(5)$

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