If you are applying V's directly to input pins thats not a good idea -
1) When device powers up possible to destroy inputs due to power sequencing issues.
2) If apply directly, same V, then OpAmp is operating open loop, so its G several hundred
thousand or more typically. But OpAmps, as stated by wwfeldman, have mismatched inputs.
This is called offset voltage. That Voff x Aol (open loop G) results in OpAmp acting like a comparator. So output would either be at - rail or + rails depending on sign of V offset.
Regards, Dana.