`color{#CCCCFF}{M i f u y u}color{#CCCCFF}{180608}` 

`x^2 - 2x = -1`

`=> x^2 - 2x + 1 = 0`

`=> (x - 1)^2 = 0`

`=> x - 1 = 0`

`=> x = 1`

Vậy `x = 1`