If the function f is derivable at x = a, then \(\mathop {{\rm{lim}}}\limits_{{\rm{x}} \to \,{\rm{a}}} \frac{{{\rm{xf}}\left( {\rm{a}} \right) - {\rm{af}}\left( {\rm{x}} \right)}}{{{\rm{x}} - {\rm{a}}}}\) equals
1
f(a) - a f'(a)
2
a f(a) - f'(a)
3
a f(a) + f'(a)
4
f'(a) - a f(a)