Z₁ = 2 + 3i; z₂ = 1 - 2i
1) z₁ + z₂ = (2 + 1) + (3i - 2i) = 3 + i
2) z₁ - z₂ = (2 - 1) + (3i + 2i) = 1 + 5i
3) z₁ * z₂ = (2 + 3i)*(1 - 2i) = 2 - 4i + 3i + 6 = 8 - i
z₁ / z₂ = (2 + 3i) / (1 - 2i) = [(2 + 3i)(1 + 2i)] / ((1 - 2i)(1 + 2i) =
= (2 + 4i + 3i - 6) / (1 + 4) = (- 4 + 7i) / 5