(2+3i)+(1-2i) = 2 + 3i + 1 - 2i = 3 + i
(2+3i)-(1-2i) = 2 + 3i - 1 + 2i = 1 + 5i
(2+3i)(1-2i) = 21 + 2(-2i) + 3i1 + 3i*(-2i) = 2 - 4i + 3i - 6i^2 = 2 - 4i + 3i + 6 = 8 - i
2+3i / 1-2i = (2+3i) / (1-2i) = ((2+3i)(1+2i)) / ((1-2i)(1+2i)) = (2+7i+6i^2) / (1+2i-2i-4i^2) = (2+7i-6) / (1+4) = -4.5 + 1.5i
(2+3i)+(1-2i) = 2 + 3i + 1 - 2i = 3 + i
(2+3i)-(1-2i) = 2 + 3i - 1 + 2i = 1 + 5i
(2+3i)(1-2i) = 21 + 2(-2i) + 3i1 + 3i*(-2i) = 2 - 4i + 3i - 6i^2 = 2 - 4i + 3i + 6 = 8 - i
2+3i / 1-2i = (2+3i) / (1-2i) = ((2+3i)(1+2i)) / ((1-2i)(1+2i)) = (2+7i+6i^2) / (1+2i-2i-4i^2) = (2+7i-6) / (1+4) = -4.5 + 1.5i