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解方程(一)

解方程(一). 2 、化简下列各式:. 2x+3x x - 0.6x + 0.3x. =(2+3)x =5x. =0.4x+0.3x =0.7x. 请你判断. 方正同学在做作业时,遇到方程 2x=5x,他将方程两边同时 除以x,竟然得到2=5!他错 在什么地方?. 等式的基本性质是什么?. 利用等式的基本性质解方程. 5 x-2=8. __________. 解:方程两边都 加上2 ,得. 5 x-2+2=8+2. _______. 5 x=8+2. 5 x=10. x=2.

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解方程(一)

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  1. 解方程(一)

  2. 2、化简下列各式: 2x+3x x-0.6x+0.3x =(2+3)x =5x =0.4x+0.3x =0.7x

  3. 请你判断 方正同学在做作业时,遇到方程 2x=5x,他将方程两边同时 除以x,竟然得到2=5!他错 在什么地方? 等式的基本性质是什么?

  4. 利用等式的基本性质解方程 5x-2=8 __________ 解:方程两边都加上2,得 5x-2+2=8+2 _______ 5x=8+2 5x=10 x=2 3x=2x+1 _______________ 解:方程两边同时减去2x,得 3x-2x=2x+1-2x ___________ 即3x-2x=1 化简,得x=1

  5. 5x -2 =8 3x = 2x + 1 3x -2x =1 5x=8 +2 你发现了什么? 把方程中的某一项改变符号后,从方程的一边移到另一边,这种变形叫移项。 想一想: 移项的依据是等式的基本性质 移项的依据是什么?移项时,应注意什么? 移项应注意:移项要变号

  6. 请你判断 1.下面的移项对不对?如果不对,应当怎样改正? (1)从5+x=10, 得x=10+5 -5 (2)从3x=8-2x, 得3x+2x=-8 8

  7. -2x + 5=4 - 3x 解 : 2x-3x =4 +5   x=9 请你判断 2.下面方程的解法对吗?如果不对,应怎样改正? 3x-2x=4-5 X=-1

  8. 例1 解下列方程 (1) (23+x+18)÷2=30 (2) 7x+9-3x=17.8 (3) x+6=3x

  9. 随堂练习 1.解下列方程: (1)(7+2.3-x)÷2=3.1 (2 ) 3+2x=5x+15 (3)10-5x=1.25-2.5x (4)2.4×5-18÷x=3

  10. 探索乐园 已知2x+1与-12x+5的值是相反数,求x的值。

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