(9.8-1.8x)×7=18.2
2个回答

解题思路:(1)等式的两边同时除以7,然后再根据等式的性质进行解答;

(2)等式的两边同时加上3.4x,然后根据等式的性质进行解答;

(3)去掉括号,把原式改写成6x-12=9-8x,然后根据等式的性质进行解答;

(4)等式的两边同时减去4x,然后根据等式的性质进行解答;

(5)去掉括号,把原式改写成5x-5=x+1,然后根据等式的性质进行解答;

(6)去掉括号,把原式改写成9x-6=11.75-0.5x,然后根据等式的性质进行解答;

(7)去掉括号,把原式改写成0.4x+1.42=0.7x-0.38,然后根据等式的性质进行解答;

(8)等式的两边同时乘上x+20,把原式改写成3(x+20)=0.6x+420,然后根据等式的性质进行解答;

(9)去掉括号,把原式改写成160-110x=91-41x,然后根据等式的性质进行解答.

(1)(9.8-1.8x)×7=18.2,

(9.8-1.8x)×7÷7=18.2÷7,

9.8-1.8x=2.6,

9.8-1.8x+1.8x=2.6+1.8x,

2.6+1.8x=9.8,

2.6+1.8x-2.6=9.8-2.6,

1.8x=7.2,

1.8x÷1.8=7.2÷1.8,

x=4;

(2)2.6x=51.6-3.4x,

2.6x+3.4x=51.6-3.4x+3.4x,

6x=51.6,

6x÷6=51.6÷6,

x=8.6;

(3)3(4x-2)-2(3x+3)=9-8x,

6x-12=9-8x,

6x-12+8x=9-8x+8x,

14x-12=9,

14x-12+12=9+12,

14x=21,

14x÷14=21÷14,

x=1.5;

(4)20+4x=6x-24,

20+4x-4x=6x-24-4x,

2x-24=20,

2x-24+24=20+24,

2x=44,

2x÷2=44÷2,

x=22;

(5)5(x-1)=x+1,

5x-5=x+1,

5x-5-x=x+1-x,

4x-5=1,

4x-5+5=1+5,

4x=6,

4x÷4=6÷4,

x=1.5;

(6)3(3x-2)=10-0.5(x-3.5),

9x-6=11.75-0.5x,

9x-6+0.5x=11.75-0.5x+0.5x,

9.5x-6=11.75,

9.5x-6+6=11.75+6,

9.5x=17.75,

9.5x÷9.5=17.75÷9.5,

x=[47/38];

(7)0.4(x-0.2)+1.5=0.7x-0.38,

0.4x+1.42=0.7x-0.38,

0.4x+1.42-0.4x=0.7x-0.38-0.4x,

0.3x-0.38=1.42,

0.3x-0.38+0.38=1.42+0.38,

0.3x=1.8,

0.3x÷0.3=1.8÷0.3,

x=6;

(8)(0.6x+420)÷(x+20)=3,

(0.6x+420)÷(x+20)×(x+20)=3×(x+20),

3(x+20)=0.6x+420,

3x+60=0.6x+420,

3x+60-0.6x=0.6x+420-0.6x,

2.4x+60=420,

2.4x+60-60=420-60,

2.4x=360,

2.4x÷2.4=360÷2.4,

x=150;

(9)35(2-x)+15(6-5x)=22x+7+21(4-3x),

160-110x=91-41x,

160-110x+110x=91-41x+110x,

69x+91=160,

69x+91-91=160-91,

69x=69,

69x÷69=69÷69,

x=1.

点评:

本题考点: 方程的解和解方程.

考点点评: 本题主要考查较难的解方程,要把方程化成一般形式,然后再根据等式的性质进行解答.