## Intermediate Algebra (6th Edition)

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The function $f(x)=\sqrt x$ is the square root function. We can take the square root of any non-negative number $x$, because we can find a number $a$ such that $a^{2}=x$. For example, $\sqrt 0=0$, because $0^{2}=0$. Also, $\sqrt 9=3$, because $3^{2}=9$ We cannot take the square root of a negative number, because there is no number that can be multiplied by itself to produce a negative number. Therefore, we can take the square root of any number greater than or equal to 0.