For some real number \(x\), \(\sqrt{x^2} \neq x\). Therefore \(x\) is :

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A negative number would work here. Suppose \(x=-1\): $$ \sqrt{x^2} \neq x $$ $$ \sqrt{(-1)^2} \neq -1 $$ $$ \sqrt{1} \neq -1 $$ $$ 1 \neq -1  \checkmark $$