15/8 + 7/ 12 - 13/3 x 3/ 8 bằng bao nhiêu. viết rõ ra luôn nha
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![](https://rs.olm.vn/images/avt/0.png?1311)
1. -x+20 = -(-15)-8+13
=> -x=15-8+13-20
=> -x=0
=> x=0
2. -(-10)+x=-13+(-9)+(-6)
=> 10+x=-13-9-6
=> x = -13-9-6-10
=> x = -38
3. 8-(-12)+10=-(-14)-x
=> 8+12+10=14-x
=> x = 14-8-12-10
=> x = -16
4. -(+12)+(-x)-(-3)=5-(-7)
=> -12-x+3=5+7
=> -x=5+7+12-3
=> -x=21
=> x=-21
5. 14-x+(-10)=-(-9)+(+15)
=> 14-x-10=9+15
=> -x=9+15-14+10
=> -x=20
=> x=-20
6. 12-(-17)+(-3)=-5+x
=> 12+17-3+5=x
=> x=31
7. x-(-19)-(+32)=14-(+16)
=> x+19-32=14-16
=> x=14-16+32-19
=> x=11
8. x-|-15|-|7|=-(-9)+|-5|
=> x-15-7=9+5
=> x=9+5+7+15
=> x=36
9. 15-x+17=13-(-21)
=> 15-x+17=13+21
=> -x=13+21-15-17
=> -x=2
=> x=-2
10. -|-5|-(-x)+4=3-(-25)
=> -5+x+4=3+25
=> x=3+25-4+5
=> x=29
![](https://rs.olm.vn/images/avt/0.png?1311)
-x + 20 = - (-15) - (8) + 13
-x + 20 = 15 - 8 + 13
-x + 20 = 7 + 13
- x + 20 = 20
x = 20 - 20
x = 0
-(-10) + x = -13 + (-9) + (-6)
10 + x = -13 - 9 - 6
10 + x = -28
x = -28 - 10
x = -38
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 4+2/5=22/5
b) 5/4+2=13/4
c) 3+3/2=9/2
d) 3/4-1/8=5/8
e) 17/15-7/10=13/30
g) 25/12-15/8=5/24
h) 5-4/3=11/3
i)15/4-3=3/4
a)\(\dfrac{4}{1}+\dfrac{2}{5}=\dfrac{20}{5}+\dfrac{2}{5}=\dfrac{22}{5}\)
b)\(\dfrac{5}{4}+\dfrac{2}{1}=\dfrac{5}{4}+\dfrac{8}{4}=\dfrac{13}{4}\)
c)\(\dfrac{3}{1}+\dfrac{3}{2}=\dfrac{6}{2}+\dfrac{3}{2}=\dfrac{9}{2}\)
d)\(\dfrac{3}{4}-\dfrac{1}{8}=\dfrac{6}{8}-\dfrac{1}{8}=\dfrac{5}{8}\)
e)\(\dfrac{17}{15}-\dfrac{7}{10}=\dfrac{34}{30}-\dfrac{21}{30}=\dfrac{13}{30}\)
g)\(\dfrac{25}{12}-\dfrac{15}{8}=\dfrac{50}{24}-\dfrac{45}{24}=\dfrac{5}{24}\)
h)\(\dfrac{5}{1}-\dfrac{4}{3}=\dfrac{15}{3}-\dfrac{4}{3}=\dfrac{11}{3}\)
i)\(\dfrac{15}{4}-\dfrac{3}{1}=\dfrac{15}{4}-\dfrac{12}{4}=\dfrac{3}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
nhóm các số có 2 chữ số với số đuôi tương tự.VD:(11-1)+(12-2)...
Chúc bạn làm đc
Bài làm:
1-2+3-4+5-6+7-8+9-10+11-12+13-14+15-16
= ( 1-2 ) + ( 3-4 ) + ( 5 -6 ) + ( 7- 8 ) + ( 9 - 10 ) + ( 11 - 12 ) + ( 13 -14 ) + ( 15-16 ) { có 8 nhóm }
= ( -1 ) + ( -1 ) + ( -1 ) + ( -1 ) + ( -1 ) + ( -1 ) + ( -1 )+ ( -1 )
= ( -1 ) . 8
= 1 ( vì các số âm là số chẵn )
Đây là bài làm của mình, mình tính theo cách tính nhanh nha
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 1-5+7-8+4-1+5-7+8
=(1-1) - (-5+5) -(7-7) -(-8+8) +4
=0
b)=-39+9
=-30
c)=(20-20)-(-4+4)-(8-8)-17+15
=-2
d)= (13-13)-(-98+98)-(91-91)-75
=-75
![](https://rs.olm.vn/images/avt/0.png?1311)
1)x=-30
2)x=-81
3)x=4
4)x=62
5)x=6
6)-13
7)-13
8)-31
9)x=-6;0;6;12
tk minh nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2.x-15=11\)
\(2x=11+15\)
\(2x=26\)
\(x=26:2\)
\(x=13\)
\(b,4.\left(2-x\right)-5\left(3-x\right)=-12\)
\(8-4x-15+5x=-12\)
\(x-7=-12\)
\(x=-12+7\)
\(x=-5\)
\(c,\left|x-7\right|+13=25\)
\(\left|x-7\right|=25-13\)
\(\left|x-7\right|=12\)
\(\Rightarrow\orbr{\begin{cases}x-7=12\\x-7=-12\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=19\\x=-5\end{cases}}\)
\(\frac{15}{8}+\frac{7}{12}-\frac{13}{3}\cdot\frac{3}{8}\)
\(=\frac{15}{8}+\frac{7}{12}-\frac{13}{8}\)
\(=\left(\frac{15}{8}-\frac{13}{8}\right)+\frac{7}{12}\)
\(=\frac{1}{4}+\frac{7}{12}\)
\(=\frac{5}{6}\)
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