Question

Anyone knows about limitation and continuity?

Answer 1

If you just plug x=1 in the expression, you can see that, as x approaches 1, the whole expression approaches the following quantity:

$\frac{\sqrt{1-y}-2}{2-1} = \frac{\sqrt{1-y}-2}{1} = \sqrt{1-y}-2$

Now, how can we find the value of y? We need some additional request. For example, if we knew that this limit had to equal 3, then we would have written

$\sqrt{1-y}-2 = 3$

and solved for y. But without something like this, we can only compute the limit and get rid of x, but y stays.