1, the establishment of constant is a mathematical concept, which means that when x takes any value in a certain interval or set u, the algebraic expression f(x) about x always satisfies 0 or more. We call it the constant compilation of "always satisfied".

2. "Invariant establishment" means that no matter how the conditions change, it is always established.

3.f(x)=ax_+bx+ 1, regardless of the value of ab, f(0)= 1 holds;

4.(x- 1)_+|y-2|=0 holds, and find the values of x and y; Because left ≥0 is a constant, it holds if and only if x= 1 and y=2.