[tex]\sqrt{x}-3=0\\\\\sqrt{x}=3\qquad\text{add 3 to both sides}\\\\\boxed{x=9}\qquad\text{square both sides}[/tex]
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2)
The expression ...
[tex]\sqrt{|x|+1}[/tex]
is defined for all values of x. The expression makes sense for all real numbers.
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Additional comment
The expression in the second question makes sense for all numbers, real or complex. The value of |x| is never negative, so the value under the radical is always positive.
