a) z1+z2 = - 1 - 3i + 2i = - 1-i
b) z1z3 = ( - 1 - 3i)( 1 - i) ==> - 1 + i - 3i + 3i^2==> - 1 - 2i - 3 ==> - 4 - 2i
c) z1+z2 /z3 = - 1 - 3i + 2i ==> (- 1 - i)(1 + i) ==> - 1 - i - i - i^2 ==> -1 -2i +1==> - 2i ==> - i
( 1 - i ) (1 - i )(1 + i ) 1 - i^2 1+1 2
d) (z1+z2)/z3 = - 1 - 3i + 2i ==> (- 1- i)(1+ i) ==> - 1 - i - i - i^2 ==> -1 -2i +1==> - 2i ==> - i
( 1 - i ) (1 - i )(1 + i ) 1 - i^2 1+1 2