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众所周知:mn+m+n+1=(m+1)(n+1) (1) mn-m-n+1=(m-1)(n-1)(2) 利用上述恒等式可以巧解某些竞赛题,下面举例说明: 例1 (1993年北京初中预赛试题)若自然数m、n满足m+n>mn,试求:m+n-mn的值.
It is known that: mn+m+n+1=(m+1)(n+1) (1) mn-m-n+1=(m-1)(n-1)(2) It is possible to solve the problem using the above identity. Some of the competition questions are as follows: Example 1 (1993 Beijing Junior High School Preliminary Test Questions) If the natural numbers m, n satisfy m+n>mn, try to find the value of m+n-mn.