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1、 小升初数学专题之解方程一.字母的运算x + 2x =1342x - x =x -35%x =x x6 + 5 =3375%x - 0.5x =3x + 4t + 5x =3a + 2.5a =25%x + 33%x =3x - x =52 733t + 4x - 2t =6x - t - x + t =7x + 6 - x =3 25二.去括号（主要是运用乘法的分配律和加减法的运算性质）1. ( + ) =a b c2. + ( + ) =a b c+ ( - ) =a b c3. a - (b + c) =a - (b - c) =应用上面的性质去掉下面各个式子的括号，能进行运算的药进行运
2、算1225 1+ ( x - ) =6 623(x -3) =(6 - x) =12 + (3+ 2x) =33381 315- (x -3) =7 - 2(x +1) =x + ( x +1) =6x -3(2x - x) =4 23111411(3x + 4) + (2x + 6) =(8x + 5) - (2x - ) =2322解方程1.运用等式的性质解简单的方程， 3x - 4 = 5解 ：3x - 4 + 4 = 5+ 43x = 5+ 4x + 5 = 7解：x + 5-5 = 7 -53x = 9x= 7 -5x = 2x = 9 3x = 3如果把画框的部分省略，我们把一个数
3、从等号的左边移到右边的过程，叫做移项，注意把一个数从方程的左边移到右边时，原来是加的变成减，原来是减的变成加号。练习5 12x -5 = 54x - 6 =1225%x - = 74x - 6 = 3x + 56 32.典型的例子及解方程的一般步骤；7 -3x =17 x =14(3x + 5) (2x -3) = 2解：7 =1+ 3x解 ：7 =14x1+ 3x = 7解 ：3x + 5 = 2(2x -3)3x + 5 = 4x - 65+ 6 = 4x -3xx =1114x = 73x = 7 -1x = 7 143x = 6x = 0.5x = 2练习317 -5x = 7213x
4、 = 73 8- 4x = 20(11x -5) (3x -1) = 343.解方程的一般步骤： 1217 1(x -3) + (x + 5) = + x6 61.去分母；（应用等式的性质，等号的两边同时乘以公分母）37 1解：3(x -3) + 2(x + 5) = 6( + x)2.去括号；（运用乘法的分配律及加减法运算律）6 63(x -3) + 2(x + 5) = 7 + x3x -9 + 2x +10 = 7 + x3x + 2x - x = 7 + 9 -104x = 63.移项；（把含有未知数的移到方程左边，不含未知数的移到方程右边）4.合并；（就是进行运算了）5.化未知数的系
5、数为 1x = 6 46.两边进行运算，看左边是否等于右边）检验（；把求出来的 的值代入方程的左右x3x =2【方程强化训练题】1223 514311(3x + 5) + (4x - 7) = + x(4 - x) - (2 - x) = 232 6234435132x + 5 =133(x + 2) =12x + = 56x = 5x + 728x = 9x -64x -3 = 2x + 350%x - 25%x = 2515%x - 25% =1.25343791 11433%x = 25%x +0.01x + 7 = 8x = 7 + xx - = x +103 3 4 6 1353 -
6、 x =7 -10x + 9 =15- 6x9 x = 369 (x - ) = 363 5 54139 ( x - ) = 36(2x + 5) (3x - 6) = 23(y +1) =12341212(5-3x) = (3- 4x)4(x + 0.5) = x + 73- 6(x - ) =133131321 2(2x + 3) - (5x -1) =12(x - ) + = 2x62 33211x - 2.8+ x = 0.74x -3+ 3x - 4 =14x - 0.2x = x + 4247(2x -1) -3(4x -1) = 5(3x + 2) -13(x - 7) - 29 - 4(2 - x) = 22