1) z1+z2=(2+3)+(5-7)i=5-2i
z1*z2=10+35+5i-7i=45-2i
2) z1-z2=7-9i
z1/z2=(3-4i)(10-5i)/(100+25)=[(30-20)-(40+15)i]/125=0.08-0.44i
3) z1*z2=(12*3/2)(cos300°+i sin300°)=9-15.6i
z1/z2=(12*2/3)(cos150+i sin150)=-6.9+4i
4) =2^9(cos(9*24)+i sin(9*24))=512(cos216+i sin216)=-414-301i