i + i11 + i21 + i31 + i41 = {i2 = -1, i4 = 1, i6 = -1, i8 = 1, i10 = -1 => i11 = -i; i21 = i*i10*i10 = i; i31 = i10*i21 = -i; i41 = i31*i10 = i} = i – i + i – i + i = i. 2) ((3-2i) (2-i)) / ((2+3i)(1+i)) = ((3-2i)(2-i)(2-3i)(1-i)) / ((2+3i)(2-3i)(1+i)(1-i)) = ((6-3i-4i-2)(2-2i-3i-3)) / ((4+9)(1+1)) = (-(4-7i)(1+5i)) / 26 = -(4+20i-7i+35) / 26 = -(39+13i)/26 = -(3+i)/2 3) (1-3i) / i = -i(1-3i)/1 = — i — 3