Question

( frac{x-1}{x+1}=frac{x+1 y-1}{n+1 y+1}, frac{(m-1)}{(n+1)+1 y} )
( left((x-1)+1 y^{1}right)left((m+1)-i y^{prime}right) )
( (n+1)^{2}-i^{2} y^{2} )
( frac{(x-1)(x+1)-i y(x-1)+i y(x+1)-c^{2} y^{2}}{(x+1)^{2}+y^{2}} )
( arctan left(frac{x-1}{2+1}right)=0 )
( frac{left(x^{2}-1right)+y^{2}}{(x+1)^{2}+y^{2}}=0 )
( m^{2}-1+y^{2}=0 )
21

# is if Ztl. a complex number sech purely imaginary, show schat that 121=1

Solution