For example, f (x) = 4x/x 2- 1. When using the discriminant method, it is wrong to write and explain the domain of X: x ≠ 1 without paying attention. Because when x takes 1, the denominator is 0. Are you still using it? This formula is meaningless. Therefore, it is necessary to determine the definition domain to make the independent variable X meaningful, and then consider the range of the dependent variable Y. (PS I forgot to log in just now ... so post the answer again ... What else can I ask for? I am a senior 3), 3, such as: f (x) = 4x/x 2-655. When using the discriminant method. If you don't pay attention to writing and explaining the domain of x: X ≠ 1 is wrong. Because when x takes 1, the denominator is 0, is it still useful? This formula is meaningless. ,0,y+(2x^2 4x/)/(x^2 2x3)+{2(x^22x)},0，