Question

谁来帮我解下方程?(80分,一道题8分)

注意5\4代表的是5分之4,在前面的是分母.我答案知道,求方程的步骤.*就代表乘.我把分数用[]框起来,以免大家搞错.[5\4]x代表5分之4乘x.这个是小学数学提高班六年级(上)里的第9课里的题目,步骤要让人容易看的懂.
1.(x+12)*[5\4]+x=42........x=18
2. [7\4]x+(90-x)*[3/2]=56.........x=56
3. [6\1]x+4=(x+4)*[4/1].............x=36
4. [5\2]x+(x+[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x........x=4500
5. x+(x+28)*[4\3]=42.....x=12
6. [19\1]x+(770-x)*[10\1]=770-720..........x=570
7. 1-[8\1]x=(1-[5\1]x)*3.........x=[19\80]
8. x=(x+[2\1]x+1)*[2\1]+20.............x=82
9. (x+2)*[3\1]+[4\1]x=24....x=40
10. (x-1)*[7\1]+1=(x-20)*[5\1].......x=22
题目抄错了,第4题4. [5\2]x+(x-[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x........x=4500.把减号写成加号了

Answer 1

这些都是一些很简单的数学运算和移项问题 

方法单一，基本上都是一模一样的 

我只说说说解题规律 

1.通分，将所有的化成整数表达式，通分就是等号两边同时乘以分母的公倍数 

2.将含有x的项移到等式的一边，常数项移到另一边 

注意移项的是有注意要添加符号，比如-x+y=5将-x移到右边，就必须在-x前添加一个符号，于是变成+x，即y=5-(-x)+x，同理将5移到左边，x-y-(5)=x-y-5=0 

也就是说移项的时候注意添加负号，还有等式两边同时加减乘除同一个数等式仍然成立

图片中给出一个例子的完全解答

Answer 2

1.(x+12)*[5\4]+x=42
(x+12)*(4/5)+x=42
相乘后得到：
[4(x+12)]/5+x=42 [4(x+12)]/5意思是：5分之4乘以(x+12)
通分后得到：
4(x+12)+5x=210
4x+48+5x=210
9x+48=210
9x=210-48
9x=162
x=18

2. [7\4]x+(90-x)*[3/2]=56
(4/7)x+(90-x)*(2/3)=56
(4/7)x+2(90-x)/3=56 2(90-x)/3意思是：3分之2乘以(90-x)
通分后得到：
12x+14(90-x)=1176
12x+1260-14x=1176
12x+1260-14x-1176=0 这步是移项
84+12x-14x=0
84-2x=0 12x-14x=-2x,这是一个负数
x=42

3. [6\1]x+4=(x+4)*[4/1
(1/6)x+4=(x+4)*(1/4)
x/6+4=(x+4)/4 (x+4)/4表示4分之x+4
通分后得到：
2x+48=3x+12
3x+12-2x-48=0 这步是移项
x-36=0
x=36

4. [5\2]x+(x+[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x
(2/5)x+[x+(2/5)x]*(1/2)+(2/5)x*[1-(1/3)]+150=x
(2/5)x+(7/5)x*(1/2)+(2/5)x*(2/3)+150=x
(2/5)x+(7/10)x+(4/15)x+150=x
12x+21x+8x+4500=30x
41x+4500=30x
11x=-4500
x=-4500/11

5. x+(x+28)*[4\3]=42
x+(x+28)*(3/4)=42
x+3(x+28)/4=42
4x+3(x+28)=166
4x+3x+84=166
7x=84
x=12

6. [19\1]x+(770-x)*[10\1]=770-720
(1/19)x+(770-x)*(1/10)=50
10x+14630-19x=9500
5130-9x=0
x=570

7. 1-[8\1]x=(1-[5\1]x)*3
1-(1/8)x=[1-(1/5)x]*3
1-(1/8)x=3-(3/5)x
40-5x=120-24x
24x-5x=120-40
19x=80
x=80/19

8. x=(x+[2\1]x+1)*[2\1]+20
x=[x+(1/2)x+1]*(1/2)+20
x=[(3/2)x+1]*(1/2)+20
x=(3/4)x+1/2+20
4x=3x+2+80
4x-3x=2+80
x=82

9. (x+2)*[3\1]+[4\1]x=24
(x+2)*(1/3)+(1/4)x=24
4(x+2)+3x=288
4x+8+3x=288
7x=280
x=40

10. (x-1)*[7\1]+1=(x-20)*[5\1]
(x-1)*(1/7)+1=(x-20)*(1/5)
5(x-1)+35=7(x-20)
5x-5+35=7x-140
5x+30+140=7x
170=7x-5x
170=2x
x=85

Answer 3

.(x+12)*[5\4]+x=42
(x+12)*(4/5)+x=42
相乘后得到：
[4(x+12)]/5+x=42 [4(x+12)]/5意思是：5分之4乘以(x+12)
通分后得到：
4(x+12)+5x=210
4x+48+5x=210
9x+48=210
9x=210-48
9x=162
x=18

2. [7\4]x+(90-x)*[3/2]=56
(4/7)x+(90-x)*(2/3)=56
(4/7)x+2(90-x)/3=56 2(90-x)/3意思是：3分之2乘以(90-x)
通分后得到：
12x+14(90-x)=1176
12x+1260-14x=1176
12x+1260-14x-1176=0 这步是移项
84+12x-14x=0
84-2x=0 12x-14x=-2x,这是一个负数
x=42

3. [6\1]x+4=(x+4)*[4/1
(1/6)x+4=(x+4)*(1/4)
x/6+4=(x+4)/4 (x+4)/4表示4分之x+4
通分后得到：
2x+48=3x+12
3x+12-2x-48=0 这步是移项
x-36=0
x=36

4. [5\2]x+(x+[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x
(2/5)x+[x+(2/5)x]*(1/2)+(2/5)x*[1-(1/3)]+150=x
(2/5)x+(7/5)x*(1/2)+(2/5)x*(2/3)+150=x
(2/5)x+(7/10)x+(4/15)x+150=x
12x+21x+8x+4500=30x
41x+4500=30x
11x=-4500
x=-4500/11

5. x+(x+28)*[4\3]=42
x+(x+28)*(3/4)=42
x+3(x+28)/4=42
4x+3(x+28)=166
4x+3x+84=166
7x=84
x=12

6. [19\1]x+(770-x)*[10\1]=770-720
(1/19)x+(770-x)*(1/10)=50
10x+14630-19x=9500
5130-9x=0
x=570

7. 1-[8\1]x=(1-[5\1]x)*3
1-(1/8)x=[1-(1/5)x]*3
1-(1/8)x=3-(3/5)x
40-5x=120-24x
24x-5x=120-40
19x=80
x=80/19

8. x=(x+[2\1]x+1)*[2\1]+20
x=[x+(1/2)x+1]*(1/2)+20
x=[(3/2)x+1]*(1/2)+20
x=(3/4)x+1/2+20
4x=3x+2+80
4x-3x=2+80
x=82

Answer 4

1.(x+12)*[5\4]+x=42........x=18
5/4x+12*5/4+x=42
5/4x+9.6+x=42
5/9x=42-9.6
5/9x=32.4
x=18
2. [7\4]x+(90-x)*[3/2]=56.........x=56
7/4x+90*3/2-3/2x=56
7/4x+60-3/2x=56
7/4x-3/2x+60=56
-21/2x=4
x=42

3. [6\1]x+4=(x+4)*[4/1].............x=36
6/1x+4=4/1x+4*4/1
6/1x+4=4/1x+1
6/1x+4-1=4/1x
12/1x=3
x=36
4. [5\2]x+(x-[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x........x=4500.
5/2x+5/3x*2/1+5/2x*3/2+150=x
5/2x+10/3x+15/4x+150=x
30/29x+150=x
30/1x=150
x=4500
5. x+(x+28)*[4\3]=42.....x=12
x+4/3x+28*4/3=42
x+4/3x+21=42
x+4/3x=21
x=12

6. [19\1]x+(770-x)*[10\1]=770-720..........x=570
19/1x+770*10/1-10/1x=50
19/1x+77-10/1x=50
19/1x-10/1x+77=50
19/1x-10/1x=127
-190/19x=127
x=570
7. 1-[8\1]x=(1-[5\1]x)*3.........x=[19\80]
8/7x=5/4x*3
x=80/19
8. x=(x+[2\1]x+1)*[2\1]+20.............x=82
2/1x+4/1x+2/1+20=x
4/3x+2/1=x
4/1x=2/1
x=2
9. (x+2)*[3\1]+[4\1]x=24....x=40
3/1x+3/2+4/1x=24
12/7x+3/2=24
12/7x=23 3/1
12/7x=3/70
x=40
10. (x-1)*[7\1]+1=(x-20)*[5\1].......x=22
7/1x-7/1+1=5/1x-4
7/1x+7/6=5/1x-4
5/1x=7/1x+7/6+4
35/2x=7/35
x=3.5

Answer 5

1.(x+12)*[5\4]+x=42
(x+12)*(4/5)+x=42
相乘后得到：
5分之4乘以(x+12)
通分 4(x+12)+5x=210
4x+48+5x=210
9x+48=210
9x=210-48
9x=162
x=18

2. [7\4]x+(90-x)*[3/2]=56
(4/7)x+(90-x)*(2/3)=56
3分之2乘以(90-x)
通分 12x+14(90-x)=1176
12x+1260-14x=1176
12x+1260-14x-1176=0 移项
84+12x-14x=0
84-2x=0 12x-14x=-2x
x=42

3. [6\1]x+4=(x+4)*[4/1
(1/6)x+4=(x+4)*(1/4)
2x+48=3x+12
3x+12-2x-48=0
x-36=0
x=36

4. [5\2]x+(x+[5\2]x)*[2\1]+[5\2]x*(1-[3\1])+150=x
(2/5)x+[x+(2/5)x]*(1/2)+(2/5)x*[1-(1/3)]+150=x
(2/5)x+(7/5)x*(1/2)+(2/5)x*(2/3)+150=x
(2/5)x+(7/10)x+(4/15)x+150=x
12x+21x+8x+4500=30x
41x+4500=30x
11x=-4500
x=-4500/11

5. x+(x+28)*[4\3]=42
x+(x+28)*(3/4)=42
x+3(x+28)/4=42
4x+3(x+28)=166
4x+3x+84=166
7x=84
x=12

6. [19\1]x+(770-x)*[10\1]=770-720
(1/19)x+(770-x)*(1/10)=50
10x+14630-19x=9500
5130-9x=0
x=570

7. 1-[8\1]x=(1-[5\1]x)*3
1-(1/8)x=[1-(1/5)x]*3
1-(1/8)x=3-(3/5)x
40-5x=120-24x
24x-5x=120-40
19x=80
x=80/19

8. x=(x+[2\1]x+1)*[2\1]+20
x=[x+(1/2)x+1]*(1/2)+20
x=[(3/2)x+1]*(1/2)+20
x=(3/4)x+1/2+20
4x=3x+2+80 4x-3x=2+80
x=82

9. (x+2)*[3\1]+[4\1]x=24
(x+2)*(1/3)+(1/4)x=24
4(x+2)+3x=288
4x+8+3x=288
7x=280
x=40

10. (x-1)*[7\1]+1=(x-20)*[5\1]
(x-1)*(1/7)+1=(x-20)*(1/5)
5(x-1)+35=7(x-20)
5x-5+35=7x-140
5x+30+140=7x
170=7x-5x
170=2x
x=85