第89页

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解:去分母,得$5(x - 1) = 10 - 2(x + 2),$去括号,得$5x - 5 = 10 - 2x - 4,$移项,得$5x + 2x = 10 - 4 + 5,$合并同类项,得$7x = 11,$系数化为1,得$x = \frac{11}{7}$
解:原方程可化为$\frac{10(x - 2)}{2} - \frac{10(x + 1)}{5} = 3,$即$5(x - 2) - 2(x + 1) = 3,$去括号,得$5x - 10 - 2x - 2 = 3,$移项,得$5x - 2x = 3 + 10 + 2,$合并同类项,得$3x = 15,$系数化为1,得$x = 5$
解:原方程可化为$\frac{2x + 5}{5} = 4 + \frac{3 + 2x}{3},$去分母,得$3(2x + 5) = 60 + 5(3 + 2x),$去括号,得$6x + 15 = 60 + 15 + 10x,$移项,得$6x - 10x = 60 + 15 - 15,$合并同类项,得$-4x = 60,$系数化为1,得$x = -15$
解:去括号,得$(\frac{1}{2}y - \frac{1}{4}) - 6 = \frac{3}{2}y - 1,$去括号,得$\frac{1}{2}y - \frac{1}{4} - 6 = \frac{3}{2}y - 1,$移项,得$\frac{1}{2}y - \frac{3}{2}y = -1 + \frac{1}{4} + 6,$合并同类项,得$-y = \frac{21}{4},$系数化为1,得$y = -\frac{21}{4}$
解 (1)小明去分母时,方程右边的“-1”未乘6,得到的方程为$2(2x - 1) = 2x + m - 1,$将$x = -\frac{3}{2}$代入,得$2[2×(-\frac{3}{2}) - 1] = 2×(-\frac{3}{2}) + m - 1,$即$2(-3 - 1) = -3 + m - 1,$$-8 = m - 4,$解得$m = -4;$
(2)正确方程为$\frac{2x - 1}{3} = \frac{2x - 4}{6} - 1,$去分母,得$2(2x - 1) = 2x - 4 - 6,$去括号,得$4x - 2 = 2x - 10,$移项,得$4x - 2x = -10 + 2,$合并同类项,得$2x = -8,$系数化为1,得$x = -4$
解: 将$x = 1$代入方程,得$\frac{2k + a}{3} = 2 + \frac{1 - bk}{6},$去分母,得$2(2k + a) = 12 + 1 - bk,$整理,得$(4 + b)k + (2a - 13) = 0,$因为无论$k$为何值,方程的解总是$x = 1,$所以$4 + b = 0$且$2a - 13 = 0,$解得$a = \frac{13}{2},$$b = -4$
1
等式的基本性质2
3
移项时没有变号
解:去分母,得$2(2x + 1) - (5x - 1) = 6,$去括号,得$4x + 2 - 5x + 1 = 6,$移项,得$4x - 5x = 6 - 2 - 1,$合并同类项,得$-x = 3,$系数化为1,得$x = -3$