Question

How can I determine the value of x that will make the expression a real √x-1

Answer 1

The content of the square root must be greater than or equal to zero. Determine the conditions on x that make this true.

As written, you require
.. x ≥ 0

If you intend
.. √(x -1) ∈ ℝ
Then
.. x -1 ≥ 0
Solve this inequality by adding 1.
.. x ≥ 1