The college entrance examination under the new curriculum standard pays more and more attention to the examination of students' comprehensive quality and application ability, and the identity problem in mathematics is a typical problem to examine students' various abilities. Because there is no fixed processing mode and thinking method for the problem of constant establishment, it has brought us a lot of trouble in various exams. These questions are generally comprehensive, which not only examines students' basic knowledge, but also examines students' ability to analyze problems and master comprehensive knowledge. How to answer this kind of questions quickly and accurately, I often use the following methods to deal with it through painstaking research. First, we high school students are familiar with quadratic function, but it is still difficult to apply quadratic function flexibly. The quadratic function is constructed in the comprehensive test questions, and the range of parameters is obtained by using the real root distribution, symmetry axis and existence of the quadratic equation. Example 1: It is known that the proposition P: the exponential function f(x)=(2a-6)x monotonically decreases on R, and the proposition Q: the two real numbers of the equation x2-3ax+2a2+ 1=0 are always greater than 3. If p or q is true and p and q are false, find the range of the number a, then 0.