It's a fundamental use and WolframAlpha appeared entirely uncooperative.
E = (4.49*10^16 Joules), m = (1 kilogram), c = (speed of light in vacuum),
and the equation:
v = (sqrt(E) c sqrt(2 c^2 m+E))/(c^2 m+E)
Give me v for the values given. Just substitute the values and calculate the result.
But I'm getting all kind of weird results. Graphs. Roots of equation where m is the variable. Definition of vacuum. "true" (yes, W.A. confirms, c does equal speed of light in vacuum).
But to substitute all the values, get a simple number, the output in meters/second? That's apparently too much to ask for. What am I doing wrong?