( Mik làm mấy phần mà bạn dưới chưa làm)

11) xy+x+y=9

\(\Leftrightarrow\) xy+x+y+1=9+1

\(\Leftrightarrow\left(xy+x\right)+\left(y+1\right)\)=10

\(\Leftrightarrow x\left(y+1\right)+\left(y+1\right)=10\)

\(\Leftrightarrow\) (x+1)(y+1)=10=1.10=10.1=-1.-10=-10.-1=2.5=5.2=-2.-5=-5.-2

\(\Rightarrow\) TH1: x+1=1 ; y+1=10

\(\Leftrightarrow x=0;y=9\)

TH2: x+1=10;y+1=1

\(\Leftrightarrow\)x=9;y=0

TH3: x+1=-1;y+1=-10

\(\Leftrightarrow\) x=-2;y=-11

...........

Vậy:........

( Bạn tự làm nốt chứ dài quá, mik chỉ hướng dẫn cách làm bài thôi)

1) -x = -7

=> x = 7

2) - x = 17

=> x = - 17

3) |x| = 17

=> x = ±17

4) -(-x) = |-17|

=> x = 17

5) - 19 - x = 17

=> - x = 17 + 19

=> x = - 36

6) - 19 - x = - 17

=> - x = - 17 + 19

=> -x = 2

=> x = - 2

7) - 5 - (10 - x) = 7

=> - 5 - 10 + x = 7

=> - 15 + x = 7

=> x = 7 + 15

=> x = 22

8) |x + 3| + 7 = 12

=> |x + 3| = 12 - 7

=> |x + 3| = 5

=> x + 3 = 5 hoặc x + 3 =- 5

=> x = 2 hoặc x = - 8

9) 2 - |x - 2| = x

=> - |x - 2| - x = - 2

TH1: x >= 2

- (x - 2) - x = - 2

=> - x + 2 - x =- 2

=> - 2x = - 4

=> x = 2 (nhận)

TH2: x < 2

-[-(x - 2)] - x = - 2

=> x - 2 - x = - 2

=> 0x = 0 (vô số nghiệm)

a) \(\frac{x}{3}=\frac{10}{15}\Leftrightarrow15x=30\Leftrightarrow x=2\)

b, \(\frac{x}{4}=\frac{9}{x}\Leftrightarrow x^2=36\Leftrightarrow\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)

c, \(\frac{5+x}{3+x}=\frac{9}{7}\left(x\ne-3\right)\Leftrightarrow35+7x=27+9x\Leftrightarrow-2x=-8\Leftrightarrow x=4\left(tmđk\right)\)

Ta có :\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)

=> \(\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)

=> \(\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)

=> \(\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)

Vì \(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\ne0\)

=> x + 20 = 0

=> x = -20

Vậy x = -20

\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)

\(\Leftrightarrow\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)

\(\Leftrightarrow\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)

\(\Leftrightarrow\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)

Vì \(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\ne0\)

\(\Rightarrow x+20=0\Rightarrow x=-20\)

\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)

\(\Rightarrow\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)\

\(\Rightarrow\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)\(\Leftrightarrow\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)

\(\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)\ne0\Rightarrow x+20=0\Leftrightarrow x=0-20=-20\)

\(\frac{x+8}{12}+\frac{x+9}{11}+\frac{x+10}{10}+3=0\)

\(\Leftrightarrow\left(\frac{x+8}{12}+1\right)+\left(\frac{x+9}{11}+1\right)+\left(\frac{x+10}{10}+1\right)=0\)

\(\Leftrightarrow\frac{x+8+12}{12}+\frac{x+9+11}{11}+\frac{x+10+10}{10}=0\)

\(\Leftrightarrow\frac{x+20}{12}+\frac{x+20}{11}+\frac{x+20}{10}=0\)

\(\Leftrightarrow\left(x+20\right)\left(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\right)=0\)

Vì \(\frac{1}{12}+\frac{1}{11}+\frac{1}{10}\ne0\)

=> \(x+20=0\)

=> \(x=-20\)

\(\frac{x+1}{10}+\frac{x+2}{9}=\frac{x+3}{8}+\frac{x+4}{7}\)

\(\frac{x+1}{10}+1+1+\frac{x+2}{9}=\frac{x+3}{8}+1+1+\frac{x+4}{7}\)

\(\Rightarrow\frac{x+11}{10}+\frac{x+11}{9}-\frac{x+11}{8}-\frac{x+11}{7}=0\)

\(\Rightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\right)\)

\(\Rightarrow\hept{\begin{cases}\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\ne0\\x+1=0\end{cases}}\)

\(\Rightarrow x=-1\)

\(\frac{x+1}{10}+\frac{x+2}{9}=\frac{x+3}{8}+\frac{x+4}{7}\)

<=> \(\left(\frac{x+1}{10}+1\right)+\left(\frac{x+2}{9}+1\right)=\left(\frac{x+3}{8}+1\right)+\left(\frac{x+4}{7}+1\right)\)

<=>\(\frac{x+11}{10}+\frac{x+11}{9}=\frac{x+11}{8}+\frac{x+11}{7}\)

<=> \(\frac{x+11}{10}+\frac{x+11}{9}-\frac{x+11}{8}-\frac{x+11}{7}=0\)

<=> \(x+11\left(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\right)=0\)

<=> x + 11 = 0  vì () \(\ne\)0

<=> x = -11

1.x=0

2.x=3

3.x=3

4,x=5

1 a x=4

b x=-4

c x=-7

d x=3

e x=10

g  x=60

h x=36

i x=16

2a 1,2,3,4,5,6,7,8,9

b 1,2,3,4,5,6,7,8,9.........

c rỗng

3a 0

b 0

c10

Bạn cho mình các bước giải được không?