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根据题意列出方程是解应用题的一个关键步骤，也是一个难点．要突破这一难关，学会寻找等量关系是关键．那么怎样寻找等量关系呢？一、妥善于抓住问题中的不变量，并利用不变量来列方程例1一船航行于A、B两个码头之间，顺水航行需3小时，逆水航行需5小时，已知水流速度是4千米
It is also a difficult point to list the equations according to the questions. To break this barrier, learning to find equal relationships is the key. So how to find the same relationship? I. Properly seize the invariants in the problem and use invariants to list the equations. Example 1 A ship is sailing between two terminals A and B. It takes 3 hours to sail through the water, and 5 hours to go against the water. Known water flow velocity It is 4 kilometers