The function \( f \) is defined below. \[ f(x)=\frac{x^{2}-11 x+28}{x^{2}-49} \] Find all values of \( x \) that are NOT in the domain of \( f \). If there is more than one value, separate them with commas. \( x=\llbracket \)

To find the values of \( x \) that are not in the domain of the function \( f(x) = \frac{x^{2}-11x+28}{x^{2}-49} \), we need to identify where the denominator is equal to zero, since division by zero is undefined. The denominator is: \[ x^{2} - 49 \] Setting it equal to zero: \[ x^{2} - 49 = 0 \] Factoring gives: \[ (x - 7)(x + 7) = 0 \] Thus, the solutions are: \[ x - 7 = 0 \quad \Rightarrow \quad x = 7 \] \[ x + 7 = 0 \quad \Rightarrow \quad x = -7 \] Therefore, the values of \( x \) that are NOT in the domain of \( f \) are \[ x = \llbracket -7, 7 \rrbracket \]