1. 解方程:
(1) $\frac{x - 0.6}{0.4} + x = \frac{0.1x + 1}{0.3}$;
(2) [2025 孝感月考] $\frac{0.4x + 2.1}{0.5} + \frac{0.5 - 0.2x}{0.03} = 0.6$。
(1) $\frac{x - 0.6}{0.4} + x = \frac{0.1x + 1}{0.3}$;
(2) [2025 孝感月考] $\frac{0.4x + 2.1}{0.5} + \frac{0.5 - 0.2x}{0.03} = 0.6$。
答案
1.【解】
(1)将小数分母化为整数分母,得$\frac {5x-3}{2}+x=\frac {x+10}{3}.$
去分母,得$15x-9+6x=2x+20.$
移项、合并同类项,得$19x=29.$
系数化为1,得$x=\frac {29}{19}.$
(2)将小数分母化为整数分母,得$\frac {4x+21}{5}+\frac {50-20x}{3}=0.6,$
去分母,得$3(4x+21)+5(50-20x)=0.6×15,$
去括号,得$12x+63+250-100x=9,$
移项,得$12x-100x=9-63-250,$
合并同类项,得$-88x=-304,$
系数化为1,得$x=\frac {38}{11}.$
(1)将小数分母化为整数分母,得$\frac {5x-3}{2}+x=\frac {x+10}{3}.$
去分母,得$15x-9+6x=2x+20.$
移项、合并同类项,得$19x=29.$
系数化为1,得$x=\frac {29}{19}.$
(2)将小数分母化为整数分母,得$\frac {4x+21}{5}+\frac {50-20x}{3}=0.6,$
去分母,得$3(4x+21)+5(50-20x)=0.6×15,$
去括号,得$12x+63+250-100x=9,$
移项,得$12x-100x=9-63-250,$
合并同类项,得$-88x=-304,$
系数化为1,得$x=\frac {38}{11}.$
2. 解方程:$\frac{2 - x}{15} + \frac{8x - 9}{14} = \frac{7x - 9}{20} + \frac{12x - 10}{21}$。
答案
2.【解】移项,得$\frac {2-x}{15}-\frac {7x-9}{20}=\frac {12x-10}{21}-\frac {8x-9}{14}.$
通分,得$\frac {8-4x}{60}-\frac {21x-27}{60}=\frac {24x-20}{42}-\frac {24x-27}{42},$
即$\frac {35-25x}{60}=\frac {1}{6}.$
去分母,得$35-25x=10.$
移项、合并同类项,得$-25x=-25.$
系数化为1,得$x=1.$
通分,得$\frac {8-4x}{60}-\frac {21x-27}{60}=\frac {24x-20}{42}-\frac {24x-27}{42},$
即$\frac {35-25x}{60}=\frac {1}{6}.$
去分母,得$35-25x=10.$
移项、合并同类项,得$-25x=-25.$
系数化为1,得$x=1.$
3. 解方程:$\frac{x - 1}{2} - \frac{2x - 3}{6} = \frac{6 - x}{3}$。
答案
3.【解】原方程可化为$\frac {x}{2}-\frac {1}{2}-\frac {x}{3}+\frac {1}{2}=2-\frac {x}{3},$
移项、合并同类项,得$\frac {x}{2}=2,$
系数化为1,得$x=4.$
移项、合并同类项,得$\frac {x}{2}=2,$
系数化为1,得$x=4.$
4. 解下列方程:
(1) $\frac{1}{2}[x - \frac{1}{2}(x + 1)] = \frac{2}{5}(x - 1)$;
(2) $2[\frac{4}{3}x - (\frac{2}{3}x - \frac{1}{2})] = \frac{3}{4}x$。
(1) $\frac{1}{2}[x - \frac{1}{2}(x + 1)] = \frac{2}{5}(x - 1)$;
(2) $2[\frac{4}{3}x - (\frac{2}{3}x - \frac{1}{2})] = \frac{3}{4}x$。
答案
4.【解】
(1)去小括号,得$\frac {1}{2}[x-\frac {1}{2}x-\frac {1}{2}]=\frac {2}{5}x-\frac {2}{5},$
去中括号,得$\frac {1}{2}x-\frac {1}{4}x-\frac {1}{4}=\frac {2}{5}x-\frac {2}{5}.$
移项,得$\frac {1}{2}x-\frac {1}{4}x-\frac {2}{5}x=-\frac {2}{5}+\frac {1}{4}.$
合并同类项,得$-\frac {3}{20}x=-\frac {3}{20}.$
系数化为1,得$x=1.$
(2)去小括号,得$2[\frac {4}{3}x-\frac {2}{3}x+\frac {1}{2}]=\frac {3}{4}x.$
去中括号,得$\frac {8}{3}x-\frac {4}{3}x+1=\frac {3}{4}x.$
移项,得$\frac {8}{3}x-\frac {4}{3}x-\frac {3}{4}x=-1.$
合并同类项,得$\frac {7}{12}x=-1.$
系数化为1,得$x=-\frac {12}{7}.$
(1)去小括号,得$\frac {1}{2}[x-\frac {1}{2}x-\frac {1}{2}]=\frac {2}{5}x-\frac {2}{5},$
去中括号,得$\frac {1}{2}x-\frac {1}{4}x-\frac {1}{4}=\frac {2}{5}x-\frac {2}{5}.$
移项,得$\frac {1}{2}x-\frac {1}{4}x-\frac {2}{5}x=-\frac {2}{5}+\frac {1}{4}.$
合并同类项,得$-\frac {3}{20}x=-\frac {3}{20}.$
系数化为1,得$x=1.$
(2)去小括号,得$2[\frac {4}{3}x-\frac {2}{3}x+\frac {1}{2}]=\frac {3}{4}x.$
去中括号,得$\frac {8}{3}x-\frac {4}{3}x+1=\frac {3}{4}x.$
移项,得$\frac {8}{3}x-\frac {4}{3}x-\frac {3}{4}x=-1.$
合并同类项,得$\frac {7}{12}x=-1.$
系数化为1,得$x=-\frac {12}{7}.$
5. 解方程:$\frac{3}{4}[\frac{4}{3}(\frac{1}{2}x - \frac{1}{4}) - 8] = \frac{3}{2}x + 1$。
答案
5.【解】去中括号,得$(\frac {1}{2}x-\frac {1}{4})-6=\frac {3}{2}x+1.$
去小括号,得$\frac {1}{2}x-\frac {1}{4}-6=\frac {3}{2}x+1.$
移项,得$\frac {1}{2}x-\frac {3}{2}x=1+6+\frac {1}{4}.$
合并同类项,得$-x=\frac {29}{4}.$
系数化为1,得$x=-\frac {29}{4}.$
去小括号,得$\frac {1}{2}x-\frac {1}{4}-6=\frac {3}{2}x+1.$
移项,得$\frac {1}{2}x-\frac {3}{2}x=1+6+\frac {1}{4}.$
合并同类项,得$-x=\frac {29}{4}.$
系数化为1,得$x=-\frac {29}{4}.$
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