Question (18):
Answer: (A) All of the following
(I am using [tex]z^*[/tex] in place of conj(z)
[tex]z*z^*=(a+ib)(a-ib)=a^2-(ib)^2= a^2+b^2=\mbox{modulus(z)}^2[/tex]
[tex]z+z^*=a+ib+a-ib=2a\\z-z^*=a+ib-a+ib=2bi[/tex]
Question (19):
Answer: (B) -7
modulus of -7 is sqrt(49)=7
the other choices are all < 7