In my text book, I came across a problem where I needed to determine the equivalent reactance of a capacitor and an inductor (its ohmic resistance is negligible). To solve my problem I started to determine the equivalent reactance of both of them and to neglect the ohmic resistance of the inductor, and I thought of doing this:
Z = √Xl²−Xc². (Where: Z is the impedance, Xl is the inductive reactance and Xc is the capacitive reactance.)
But in the problem statement, Xc is 3Xl. So, putting them in the above equation is like:
Z =√Xl²-9Xl² =√-8Xl²
Which has no sense because of the negative sign. So my question is: What would be the equivalent reactance of an inductive and capacitive reactance? Is my approach correct but missing something, or it is wrong?