To solve the equation \( x^2 + 9 = 45 \), we start by isolating \( x^2 \):
\[ x^2 + 9 = 45 \]
Subtracting 9 from both sides:
\[ x^2 = 45 - 9 \] \[ x^2 = 36 \]
Next, we take the square root of both sides to find \( x \):
\[ x = \pm \sqrt{36} \] \[ x = \pm 6 \]
This gives us the solutions \( x = 6 \) and \( x = -6 \). Thus, the solution set is:
\[ {-6, 6} \]
Amelia is correct in stating that the solution set is \({-6, 6}\). Therefore, the answer is:
Amelia.