lf `z(!=-1)` is a complex number such that `[z-1]/[z+1]` is purely imaginary, then `|z|` is equal to

Explanation

Given,
Let z=x+iy


`(z−1)/(z+1)​=
(x+iy−1)/(x+iy+1)​+(x-iy+1)/(x-iy+1)​
`

=
`(z−1)/(z+1)​=(x^2−iyx+x+iyx+y^2+iy−x+iy−1​)/((x+1)^2+y^2)`

...