Question 915864
You can complete the square.
{{{RI^2+VI-P=0}}}
{{{I^2+(V/R)I-P/R=0}}}
{{{I^2+(V/R)I+(V/(2R))^2-(V/(2R))^2-P/R=0}}}
{{{(I+V/(2R))^2=(V/(2R))^2+P/R}}}
{{{I+V/(2R)=0 +- sqrt((V/(2R))^2+P/R)}}}
{{{I=-V/(2R) +- sqrt((V/(2R))^2+P/R)}}}