To solve the equation \(-x^2 - 3.5 = -12.5\), let's first isolate the term involving \(x\):
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Start by adding \(3.5\) to both sides of the equation: \[ -x^2 = -12.5 + 3.5 \] \[ -x^2 = -9 \]
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Now, multiply both sides by \(-1\): \[ x^2 = 9 \]
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Take the square root of both sides: \[ x = \pm 3 \]
Thus, the solutions are \(x = -3\) and \(x = 3\), which can be expressed as the set \({-3, 3}\).
The correct answer is: \({−3,3}\)