Initially, the observer is at rest relative to the light source. Then
the light source emits light towards the observer and this light has
frequency f, wavelength L and speed c relative to both light source
and observer. Before the light reaches the observer, the observer
starts moving towards the light source with constant speed v.
Accordingly, the speed of light relative to the observer automatically
becomes c'=c+v and the frequency the observer will measure is:

f'=c'/L=(c+v)/L or 2+2=4

No, teach Einsteinians for 100 years. The wavelength remains constant
relative to the light source but varies with v relative to the
observer so that the speed of light remains constant relative to both
light source and observer. The frequency the observer will measure is:

f'=c/L' or 2+2=5

http://www.online-literature.com/orwell/1984/ George Orwell "1984":
"In the end the Party would announce that two and two made five, and
you would have to believe it. It was inevitable that they should make
that claim sooner or later: the logic of their position demanded it.
Not merely the validity of experience, but the very existence of
external reality, was tacitly denied by their philosophy. The heresy
of heresies was common sense. And what was terrifying was not that
they would kill you for thinking otherwise, but that they might be
right. For, after all, how do we know that two and two make four? Or
that the force of gravity works? Or that the past is unchangeable? If
both the past and the external world exist only in the mind, and if
the mind itself is controllable what then?"

Pentcho Valev