I know how to do the work I just don't understand why we should use -i to calculate the power and reactive factors. It would be great if someone could help me out! My thinking is along the lines of "Because the power is negative the and the component is following the sign convention the voltage or the current are negative (not really negative since this is AC. I don't really know how to describe it). Anyway because of that assumption we could either multiply the current by -1 or the voltage by negative 1 and here they chose to use the current to multiply by -1."