To solve the equation \( x^2 = 81 \) by inspection, we need to determine which values of \( x \) make this equation true.
Taking the square root of both sides, we have: \[ x = \pm \sqrt{81} \]
Calculating the square root, we find: \[ \sqrt{81} = 9 \]
Thus, the solutions for \( x \) are: \[ x = 9 \quad \text{and} \quad x = -9 \]
Therefore, the complete solution set is: \[ { -9, 9 } \]
So the correct response is: \({−9, 9}\) (left brace negative 9 comma 9 right brace)