The fraction x2 + 2x of 1, when x takes what value is meaningful

The fraction x2 + 2x of 1, when x takes what value is meaningful

(2x) / (x2 + 1) denominator cannot be equal to 0x2 + 1 ≠ 0x2 ≠ - 1, because x2 ≥ 0, so x takes any value