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一、错用合并同类项法则例1合并同类项:(3x-2y)-(4x+5y).错解原式:3x-2y-4x-5y=-1-7=-8.分析3x-4x应为-x,而不是-1;同样-2y-5y应为-7y,而不是-7.本例错在把同类项系数相加时,忘记了“字母与相同字母的指数保持不变”.正解原式:-x-7y.二、不是同类项,却盲目合并例2合并同类项:7x~2y-5xy~2+4yx~2.错解:原式=2x~2y+4yx~2=6x~2y.分析本例错在对同类项概念理解不清楚.这里的
First, the misuse of the merger of similar items Example 1 merge the same items: (3x-2y) - (4x +5 y). The original solution: 3x-2y-4x-5y = -1-7 = -8 Analysis 3x- 4x should be -x, instead of -1; the same -2y-5y should be -7y, not -7. This example is wrong in the sum of the same type of coefficient, forget the “letters and letters of the same index remain unchanged Change ”. Positive solution Original: -x-7y. Second, not the same items, but the blind merger Example 2 Merge the same items: 7x ~ 2y-5xy ~ 2 + 4yx ~ 2. The wrong solution: the original = 2x ~ 2y + 4yx ~ 2 = 6x ~ 2y.Analysis of this case is wrong in understanding the concept of similar items is not clear here.