Question
If $f(x) = 3x^2 + 3$ then for which value of $x, f’(x) = f(x)?$

Answer

Here, $f(x) = 3x^2 + 3$
$\therefore f'(x) = 6x + 0 = 6x$
Now, $f’(x) = f(x)$
$6x = 3x^2 + 3$
$\therefore 3x^2 – 6x + 3 = 0$
$\therefore x^2 – 2x + 1 = 0$
$\therefore (x - 1)^2 = 0$
$\therefore (x - 1) (x - 1) = 0$
$\therefore x = 1$
Hence, if $x = 1$, then $f’(x) = f(x).$

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