有些复杂的数字问题竞赛题。由于数字太大，式子冗长，令人望而生畏，这时若能冷静观察仔细分析，巧用字母替换数字，常常能使问题化难为易，迅速获解，试举几例说明．例1计算：1992×19941994－1994×19931993＝．（94年“希望杯”全国数学邀请赛初一试题）解设x＝1994，则（9 Some complex digital game problems. Because the numbers are too large and the formulas are lengthy and daunting, if we can observe them carefully and carefully and use letters to replace numbers, we can often make problem-solving difficult and easy to solve. We will quickly explain and explain a few examples. Example 1 calculation: 1992×19941994-1994×19931993=. (The “Hope Cup” National Mathematics Invitational Tournament of the First Year of the 94th Test) Solution x=1994, then (9