1-1i is a complex number. It is the result of the subtraction of the imaginary number 1i from the real number 1. 1 is just 1. 1i is another way of writing 1*i, which is just i. i is the square root of -1, and I don't care if that does not make sense. Like all complex numbers, it can be represented as a dot on the plane. If we will pick the x-axis to represent the real part of the number and to go from left to right, and the y-axis to represent the imaginary part of the number and to go from down to up, then 1-1i will be a bit right and a bit down from the zero of the plane, which is at 0+0i. Its distance from the zero will be about 1.4142. The fifth power of 1-1i is equal to minus four time 1-1i, and if you think that's weird, just wait till I'll tell you about j and k.