For differentiability,

LHD(at x = 3) = RHD (at x = 3)

(LHD at x = 3) =

=

=

=

=

= 12

(RHD at x = 3) =

=

=

=

=

=

= 12

Since, (LHD at x = 3) = (RHD at x = 3)

Hence, f(x) is differentiable at x = 3.