Question

Positive square root of 81

Answer 1

$x \ \textgreater \ 0 \\ \\ x= \sqrt{81} \ \ \ | (...)^{2} \\ \\ x^{2}=81 \\ \\ x^{2}-81=0 \\ \\ (x-9)(x+9)=0 \\ \\ x-9=0 \ \vee \ x+9=0 \\ \\ \boxed{x=9} \ \vee \ x=-9 \not\in D$

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Answer 2

$\sqrt{81} = +/-9 \\ (-9)^{2} =81 \\ (9)^{2} = 81$
The square root of 81 is 9. Therefore, the positive square root of 81 is positive 9.

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