Constant holds, that is, an algebraic expression always holds within a given range, for example: x? 0? 5≥0 holds in the real number range of x∈R, that is, an algebraic expression holds in a given range, and the values holding the algebraic expression may be one, two or infinite, that is, the number is indefinite, and there may or may not be such values in this given range, for example, X. 0 can be accommodated in x & gt-2. To be exact, an algebraic expression is true in a given range, or it is true only in this range, and the values outside this range cannot be true, but the values in this algebraic expression can be true. For example: (x- 1)? 0? 5=0, which holds when x= 1 It can be said that when a constant remains true, it will certainly remain true in a given range, but the condition that the constant remains true may also conform to the algebraic expression outside the given range, that is, the constant remains true does not necessarily contain all the values that satisfy this algebraic expression, but it does contain all the values that satisfy this algebraic expression, and all the given ranges also satisfy this algebraic expression. 0 in x >; -5 can hold, when x> is at-1, it is exactly true and unchanged, while at-1 < x<9 is constant, but it is not completely correct.