Hello, ceasar_19134!

If the reciprocal ofx + 1isx - 1, determinex

. . . . . . . . . . . . . . .1

The equation is: . ------- .= . x - 1

. . . . . . . . . . . . . x + 1

Assuming x ≠ -1, multiply both sides by (x + 1): . 1 .= .(x + 1)(x - 1)

- - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ._

And we have: . x² - 1 .= .1 . → . x² .= .2 . → . x .= .±√2