Also
lim
( )
x
c f x
→
 = lim (
)
–
x
c
x
c
→
−
=
          (Why )
Since lim
( )
( )
x
c f x
f c
→
=
,  f  is continuous at all negative real numbers Now, let c be a real number such that c > 0 Then f (c) = c