\frac{(x+iy)(a-ib)}{(a-ib)(a+ib)}
=\frac{xa-ixb+iya+yb}{(a-ib)(a+ib)}
Taking the conjugate we get
=\frac{xa+yb-i(ya-xb)}{(a-ib)(a+ib)}
=\frac{a(x-iy) -ib(x-iy)}{(a-ib)(a+ib)}
=\frac{x-iy}{a-ib}
as required
for 15 sketch it out if it helps visualise the situation and use dot product
theres quite a few different ways u could do 16 but the most reasonable one imo is to also just sketch it out and get an inequality from that
are there any textbooks that are recommended to follow along with the videos for practice questions like how mcgrathematics follows the cambridge textbook for maths?
would this not have 2 complex solutions?
3x^2 +4x+2i = 0
x=\frac{-4 \pm \sqrt{16-24i}}{6}
\text{Let } \sqrt{16-24i}=a+bi, \text{where a and b are real numbers}
\text{From this we have, } a^2 - b^2 = 16 \text{ and, } ab = -12
\text{Rearranging the second term as } b=\frac{-12}{a},
a^2 -...
instead of letting z_{k}=x+iy u could just leave it as z_{k}
LHS=|z_{k+1}|
=\left|z_{k}\left(1+\frac{i}{|z_{k}|}\right)\right|
=\left|z_{k}\left(\frac{|z_{k}|+i}{|z_{k}|}\right)\right|
=||z_{k}|+i|
Using assumption
=|\sqrt{k}+i|
Since \sqrt{k} is real and i is imaginary...
the difference in arguments would be zero (just do lhs-rhs) so they are collinear. if z is in between 1 and -1, the argument is pi not 0 (you can see this by either testing values or drawing it out).