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学完代入消元法和加减消元法后,老师出了这样一道题: 解方程组: 他让同学们八仙过海,各显神通,只要能消元,不论采用什么方法都可以. 首先是张兰眼明手快,一眼发现方程①中y的系数为1,于是抢着发言:“可以用代入法消元,由①,得y=2x+9, ③把③代入②消去y,得3(2x+9-7)=2(x-3),解之,得x=-3,代入③得y=3. ∴. 师:这样消元好!好在能发现y
After learning to substitute the elimination method and the addition and subtraction elimination method, the teacher asked the following question: Solution equation group: He asked his classmates to cross the sea and show their supernatural powers. As long as they can eliminate the yuan, no matter what method is adopted, the first is Zhang. Lan is quick-handed. At first glance, he finds that the coefficient of y in equation 1 is 1, so he rushes to speak: “You can use substitution method to eliminate the yuan, from 1, get y=2x+9, 3 replace 3 to 2 to get y, get 3(2x+ 9-7) = 2 (x - 3), solution, get x = -3, and substitute 3 for y = 3. ∴ 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师 师.