I had a few doubts in mind. Please help. 1) Is -15 the L.C.M. of -5 and -3? 2) Can all complex numbers be plotted in a number line. 3) 1^(1/3)= 1, ω, ω^2, where ω= -(1/2)+i[3^(1/2)/2] Then, if we plot these 3 values along a number line, will we get 3 different points or will it be the same point? 4) I don't get the use of complex numbers. I mean, they don't even exist, right? Isn't that why we write √-1=i ?