Examining the equation
We have 2 terms:
and

For the sum of these to equal a negative number, in this case -3, one of these terms would have to be negative.
So what's the problem?
The function
(square root of x) only returns positive values!
(See the attached image for a graph of
)
Since neither of the terms can be negative, it can't be equal to -3. In other words, no matter what we put as
, we can't solve the solution, so we say that the equation does not have any solutions.