Question

I don't know what I can't get right here!
(a-ib)^2 = 4i

Show that ab= 2

Answer 1

\[a ^{2}-i(2ab)-b ^{2} = 0+4i\]

Answer 2

\[-2ab = 4\]

\[ab=-2 ?\]

Answer 3

thats correct.
now compare real and imaginary parts

Answer 4

yes, ab is indeed -2
it cannot be +2

Answer 5

that's what I did , and i got ab =-2

Answer 6

yes, and i said ab =-2,

Answer 7

for imaginary numbers

Answer 8

thanx. it was an exam question

Answer 9

ok, welcome ^_^
and you were absolutely correct :)