10. (1-4i)+(1+7i)= 1-4i+1+7i= 1+1-4i+7i=2+3i
11. -1-3i+2-2i=1-5i
12. (3+4i)*(3-2i)=9+12i-6i-8(i^2)=9+6i+8= 15+6i (i^2=-1!!!!!)
13. (1+3i)/(-2-i)= (1+3i)*(-2+i)/(-2-i)*(-2+i)=-2-6i+i-3/4+1=-5-5i/5=5(-1-i)/5=-1-i
14. (3+2i)^3=
модель: (a+b)^3=a^3+3a^2*b +3a*b^2+b^3