Official solution
f : R \[ \to \] R, with f(0) = f(1) = 0
and f'(0) = 0
\[ \because \] f(x) is differentiable and continuous
and f(0) = f(1) = 0
Applying Rolle's theorem in [0, 1] for function f(x)
f'(c) = 0, c \[ \in \] (0, 1)
Now again
\[ \because \] f'(c) = 0, f'(0) = 0
again applying Rolles theorem in [0, c] for function f'(x)
f''(c1) = 0 for some c1 \[ \in \] (0, c) \[ \in \] (0, 1)