Answer
The solution is $\left\{-1, 3\right\}$.
Work Step by Step
Take the square root of both sides to obtain:
$x-1 = \pm \sqrt{4}
\\x-1= \pm \sqrt{2^2}
\\x-1 = \pm 2$
Add 1 to both sides to obtain:
$x = 1 \pm 2$
Split the solutions to obtain:
$x_1 = 1+2 = 3
\\x_2 = 1-2 = -1$
Thus, the solution is $\left\{-1, 3\right\}$.
