数学竞赛中常遇到一类给出条件的求值计算问题.如果直接代入计算,势必相当繁琐.但若能对题设条件作些适当变形,然后利用常数代换,则可巧妙求解.下面以近两年来的竞赛试题为例予以说明. Mathematical competitions often encounter a class of calculations that give conditions for evaluation. If they are directly substituted into the calculations, they will be quite cumbersome. However, if you can make some appropriate distortions to the terms and then use constant substitutions, you can solve them cleverly. Two years of contest questions as an example to illustrate.