9. Tìm x biết 

a x- ( 12- 15)= -8

<=> x - 12 + 15 = -8

<=> x + 3 = -8

<=> x = -11

Vậy x = -11

b. (x- 29 )- ( 17- 38)= -9

<=> x - 29 - 17 + 38 = -9

<=> x - 8 = -9

<=> x = -1

Vậy x = -1

a) x-12+15=-8

=>x=-8-15+12

=>x=-11

Vậy x=-11

b)x-29+21=-9

=>x=-9-21+29

=>x=-1

Vậy x=-1

a) Ta có: x-(12-15)=-8

\(\Leftrightarrow x-12+15=-8\)

\(\Leftrightarrow x+3=-8\)

hay x=-8-3=-11

Vậy: x=-11

b) Ta có: \(\left(x-29\right)-\left(17-38\right)=-9\)

\(\Leftrightarrow x-29-17+38+9=0\)

\(\Leftrightarrow x+1=0\)

hay x=-1

Vậy: x=-1

Ta có : 

\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-..-\frac{20}{53.55}=\frac{3}{11}\)

\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{52.55}\right)=\frac{3}{11}\)

Đặt \(A=\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\)

\(A=10\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+...+\frac{2}{53.55}\right)\)

\(A=10\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\)

\(A=10\left(\frac{1}{11}-\frac{1}{55}\right)\)

\(A=10.\frac{4}{55}=\frac{40}{55}=\frac{8}{11}\)

=> \(x-\frac{8}{11}=\frac{3}{11}\)

\(x=\frac{3}{11}+\frac{8}{11}=\frac{11}{11}=1\)

Ủng hộ mk nha !!! ^_^

 I don't no
 

\(7x-2x=6^{17}:6^{15}+\dfrac{44}{11}\)

= \(7x-2x=6^{17}:6^{15}+4\)

= \(7x-2x=6^{17}:6^{15}+4\)

=\(7x-2x=6^2+4\)

=\(7x-2x=36+4\)

= \(7x-2x=40\)

=> x.(7-2)= 40

=> x.5=40

=> x=8

a) x−(−15)=−13−(−85−13)

=> x+15=85

=>x=70

b) (−9−x)+(x−14)=17−(−8+x)

=>-9-x+x-14=17+8-x

=>-23=25-x

=>x=48

a, x=70

b,x=48

kick nha

a) x−(−15)=−13−(−85−13)

=> x+15=85

=>x=70

b) (−9−x)+(x−14)=17−(−8+x)

=>-9-x+x-14=17+8-x

=>-23=25-x

=>x=48

[ chúc bạn học tốt ]

\(\frac{x+22}{11}+\frac{x+23}{12}=\frac{x+24}{13}+\frac{x+25}{14}\)

\(\Leftrightarrow\left(\frac{x+22}{11}+1\right)+\left(\frac{x+23}{12}+1\right)=\left(\frac{x+24}{13}+1\right)+\left(\frac{x+25}{14}+1\right)\)

\(\Leftrightarrow\frac{x+33}{11}+\frac{x+35}{12}=\frac{x+37}{13}+\frac{x+39}{14}\)

\(\Leftrightarrow\frac{x+33}{11}+\frac{x+35}{12}-\frac{x+37}{13}-\frac{x+39}{14}=0\)

\(\Leftrightarrow\frac{2184\cdot\left(x+33\right)+2002\cdot\left(x+35\right)-1848\cdot\left(x+37\right)-1716\cdot\left(x+39\right)}{24024}=0\)

\(\Leftrightarrow2184x+72072+2002x+70070-1848x-68376-1716x-66924=0\)

\(\Leftrightarrow622x+6842=0\)

\(\Leftrightarrow x=-11\)

2-x=17-(-5)

2-x=17+5

2-x=22

x=2-22

x=-20

a) 2 - x = 17-(-5)    

2-x = 17+5

x= 2- 22

x= -20 

b) x - 12 = (-9) - 15

x-12 = -21

x= -21+12

x= -9

\(a.-20\\ b.-12\)

\(-12-13+x=-15+17\)

\(-25+x=2\)

\(x=2-\left(-25\right)=2+25=27\)

cà khịa time x=+
 

cân cặc

=2100190