Z1+z2= 2+i+(-1+2i) =1+3i
z1-z2= 2+i - (-1+2i) = 2+i +1-2i =3 - i
z1*z2= (2+i)*(-1+2i) =-2-i+4i+2i²= -2-i+4i +2*(-1) = -4+3i
(2+i) (2+i) (2+i)*(2i +1) 4i+2i²+2+i 4i+2*(-1)+2+i
z1:z2= ----------- = ----------- = ------------------- = ---------------- = ------------------ =
(-1+2i) (2i -1) (2i -1)(2i +1) (2i)²-1² 4(-1) -1
5i
= ----------- = - i
-5