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BÀI 1: Tính
1) -(-10)-(+14)=10-14=-4
2) -(+15)-12=-15-12=-27
3) (-11)-(-13)=-11+13=2
4) -(-13)-(-10)=13+10=23
5) -4-(+7)=-4-7=-11
Bài 2 : tìm x:
a)x+(-5)=-(-7)
x=7+(-5)
x=2
vậy x=2
b)x-8=-(+10)
x-8=10
x=10+8
x=18
vậy x=18
c)x-(-12)=14
x+12=14
x=14-12
x=2
vậy x=2
d)x-(+3)=-17
x-3=17
x=17+3
x=20
vậy x=20
e)x+20=-(-23)
x+20=23
x=23-20
x=3
vậy x=3
BÀI 3:tính
a)17-(-9)-(+25)
=17+9-25
=26-25
=1
b)-[-13]-15+(-20)
=13-15-20
=-2-20
=-22
c)-17-(-16)-23
=-17+16-23
=-1-23
=-24
d)-(-25)-(-14)+(-17)
=25+14-17
=39-17
=22
cảm ơn bạn rất nhiều chúc bạn và gia đình mạnh khỏe, vui vẻ bên nhau và cùng đón 1 cái TẾT vui vẻ!
HAPPY NEW YEAR
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a) \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
\(\Leftrightarrow\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}\)
\(\Leftrightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)
Vì \(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\ne=\)
Nên x + 1 = 0 => x = -1
b) \(\frac{x+1}{14}+\frac{x+2}{13}=\frac{x+3}{12}+\frac{x+4}{11}\)
\(\Leftrightarrow\frac{x+1}{14}+1+\frac{x+2}{13}+1=\frac{x+3}{12}+1+\frac{x+4}{11}+1\)
\(\Leftrightarrow\frac{x+15}{14}+\frac{x+15}{13}=\frac{x+15}{12}+\frac{x+15}{11}\)
\(\Leftrightarrow\frac{x+15}{14}+\frac{x+15}{13}-\frac{x+15}{12}-\frac{x+15}{11}=0\)
\(\Leftrightarrow\left(x+15\right)\left(\frac{1}{14}+\frac{1}{13}-\frac{1}{12}-\frac{1}{11}\right)=0\)
Vì \(\frac{1}{14}+\frac{1}{13}-\frac{1}{12}-\frac{1}{11}\ne0\)
Nên x +15 = 0 => x = -15
a,\(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
\(\Rightarrow\left(x+1\right).\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}\right)=\left(x+1\right).\left(\frac{1}{13}+\frac{1}{14}\right)\)
\(\Rightarrow\left(x+1\right).\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}\right)-\left(x+1\right).\left(\frac{1}{13}+\frac{1}{14}\right)=0\)
\(\Rightarrow\left(x+1\right).\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)
Vì \(\frac{1}{10}>\frac{1}{13};\frac{1}{11}>\frac{1}{14}\Rightarrow\frac{1}{10}+\frac{1}{11}>\frac{1}{13}+\frac{1}{14}\Rightarrow\frac{1}{10}+\frac{1}{11}+\frac{1}{12}>\frac{1}{13}+\frac{1}{14}\)
\(\Rightarrow\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}>0\)
\(\Rightarrow x+1=0\Rightarrow x=-1\)
b, Bạn cộng thêm 1 vào \(\frac{x+1}{14};\frac{x+1}{13};\frac{x+1}{12};\frac{x+1}{11}\)Mội bên phân số 1 đơn vị rồi áp dụng như bài 1
![](https://rs.olm.vn/images/avt/0.png?1311)
A = ( -4/5 + 4/3 ) + (-5/4 + 14/5) - 7/3
= 8/15 + 31/20 - 7/3
= 25/12 - 7/3
= -1/4
B = 8/3 x 2/5 x 3/8 x 10x 19/92
= 16/15 x 15/4 x 19/92
= 4x19/92
= 19/23
![](https://rs.olm.vn/images/avt/0.png?1311)
Cái dề, bài này giúp á, tính ra là ok mà
(13/10x - 15).(-5/14) = 3
13/10x - 15 = 3 : (-5/14)
13/10x - 15 = 3 x (-14/5)
13/10x - 15 = -42/5
=> 13/10x = -42/5 + 15
=> 13/10x = 33/5
=> x = 33/5 : 13/10
=> x = 33/5 x 10/13
=> x = 66/13
bn tự lm típ, tính ra là ok mà
![](https://rs.olm.vn/images/avt/0.png?1311)
a,\(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
= \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}\)
\(\Rightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)\)
Vì 10<11<12<13<14 \(\Rightarrow\frac{1}{10}>\frac{1}{11}>\frac{1}{12}>\frac{1}{13}>\frac{1}{14}\)
\(\Rightarrow\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}>0\)
\(\Rightarrow x+1=0\)
\(\Rightarrow x=-1\)
b, \(\frac{x+4}{2000}+\frac{x+3}{2001}=\frac{x+2}{2002}+\frac{x+1}{2003}\)
\(=\left(\frac{x+4}{2000}+1\right)+\left(\frac{x+3}{2001}+1\right)=\left(\frac{x+2}{2002}+1\right)\)\(+\left(\frac{x+1}{2003}+1\right)\)
\(=\frac{x+2004}{2000}+\frac{x+2004}{2001}=\frac{x+2004}{2002}+\frac{x+2004}{2003}\)
\(=\frac{x+2004}{2000}+\frac{x+2004}{2001}-\frac{x+2004}{2002}-\frac{x+2004}{2003}=0\)
\(=\left(x+2004\right)\left(\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}-\frac{1}{2003}\right)=0\)
\(\Rightarrow x+2004=0\)
\(\Rightarrow x=-2004\)
đề rối
\(x+\frac{3}{10}+x+\frac{3}{11}+x+\frac{3}{12}=x+\frac{3}{13}+x+\frac{3}{14}\)
\(\Leftrightarrow3x+\left(\frac{3}{10}+\frac{3}{11}+\frac{3}{12}\right)=2x+\left(\frac{3}{13}+\frac{3}{14}\right)\)
\(\Leftrightarrow3x+\frac{181}{220}=2x+\frac{81}{182}\)
\(\Leftrightarrow3x-2x=-\frac{181}{220}+\frac{81}{182}\)
\(\Leftrightarrow x=-\frac{181}{220}+\frac{81}{182}=\frac{-7561}{20020}\)
hay là
\(\frac{x+3}{10}+\frac{x+3}{11}+\frac{x+3}{12}=\frac{x+3}{13}+\frac{x+3}{14}\)
\(\Leftrightarrow\frac{x+3}{10}+\frac{x+3}{11}+\frac{x+3}{12}-\frac{x+3}{13}+\frac{x+3}{14}=0\)
\(\Leftrightarrow\left(x+3\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}+\frac{1}{14}\right)=0\)
\(\Leftrightarrow x+3=0\)( vì \(\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}+\frac{1}{14}\right)\ne0\))
\(\Rightarrow x=-3\)