A piecewise function, with 2 segments constructed by a line passing (-5,1), (-3,2), and (-1,4) and a line passing (-1,5), (3,3), and (5,1), as shown in the figure. Let $f$ be the function given by the following graph. What is the domain of $f$? 

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: A piecewise function, with 2 segments constructed by a line passing (-5,1), (-3,2), and (-1,4) and a line passing (-1,5), (3,3), and (5,1), as shown in the figure. Let $f$ be the function given by the following graph. What is the domain of $f$? 

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: A piecewise function, with 2 segments constructed by a line passing (-5,1), (-3,2), and (-1,4) and a line passing (-1,5), (3,3), and (5,1), as shown in the figure. Let $f$ be the function given by the following graph. What is the domain of $f$? 
