Question 175234
the student is wrong.
here's why.
{{{sqrt(-x) = 3}}}
is the original equation.
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if you square both sides of the equation you get:
{{{(sqrt(-x))^2 = 3^2}}} which becomes:
-x = 9 which becomes x = -9 once you multiply both sides of the equation by (-1).
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to prove the answer is correct you substitute the value of -9 for x in the original equation.
{{{sqrt(-(-9)) = 3}}}
which becomes:
{{{sqrt(9) = 3}}}
which becomes:
3 = 3 proving the value of x = -9 is good.
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i believe the student was reacting to the fact that there was a negative sign under the square root and you can't take the square root of a negative number.
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if x is negative, however, than a minus of a minus is a plus making the solution valid.
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