Hi,
there are several "issues" here. First of all
(x - 50000)^4.51846
is complex for x<50000, e.g.
(x - 50000)^4.51846 /. x -> 2
is -9.88935*10^19 + 1.70333*10^21 I.
Plot does not plot complex numbers.The "interesting part of your graph is for x>50000.
Also, you should plot f[x] instead of "f".
f[x_] := ((x - 50000)^4.51846) (E^(50000 - x)) (4.6924^-7)
Plot[f[x], {x, 50000, 50050}, PlotRange -> All]
does work and gives a reasonable output:
So, if you plot it for x< 50000 it will not produce a useful output, because the Plot function is not made to plot complex functions.
Furthermore, the values that you want to plot are insanely large. Look at this:
Table[Evaluate[f[x]], {x, 0, 5}]
{-1.046106944790515*10^21730 +
1.801802763355185*10^21731 I, -3.848064616838928*10^21729 +
6.627862949115713*10^21730 I, -1.415495933981097*10^21729 +
2.438034178117325*10^21730 I, -5.206847948258534*10^21728 +
8.968215982373779*10^21729 I, -1.915319207666480*10^21728 +
3.298924128423410*10^21729 I, -7.045428821964528*10^21727 +
1.213496687279907*10^21729 I}
In the interesting regime 50000<x<50050 the values are very small. It will be difficult to have a reasonable representation over the entire domain.
Cheers,
Marco