a: Ta có: \(\dfrac{x-2}{x-1}=\dfrac{x+4}{x+7}\)

\(\Leftrightarrow x^2+5x-10=x^2+3x-4\)

\(\Leftrightarrow2x=6\)

hay x=3

Chọn C

Đặt \(\frac{x-18}{x+4}=\frac{x-17}{x+16}=k\)

Suy ra: \(x-18=k\left(x+4\right)\Rightarrow x=\frac{4k+18}{1-k}\left(1\right)\\ x-17=k\left(x+16\right)\Rightarrow x=\frac{16k+17}{1-k}\left(2\right)\)

Từ (1) và (2) ta được: \(4k+18=16k+17,\) suy ra \(k=\frac{1}{12},x=20\)

C

C

18 . (x-16) = 18

x - 16 = 18 : 18 

x - 16 = 1

x = 16 + 1

x = 17 

Đáp án : C

Dễ lắm bạn ạ 

\(\frac{x-18}{x+4}=\frac{x-17}{x+16}\)

\(\Leftrightarrow\left(x-18\right)\left(x+16\right)=\left(x+4\right)\left(x-17\right)\)

\(\Leftrightarrow x^2+16x-18x-288=x^2+4x-17x-68\)

\(\Leftrightarrow x^2-2x-288=x^2-13x-68\)

\(\Leftrightarrow x^2-x^2-2x+13x=-68+288\)

\(\Leftrightarrow11x=220\)

\(\Leftrightarrow x=20\)

(x-18)(x+16)=(x+4)(x-17)

x²-2x--288=x²-13x-68

x²-x²-2x+13x-288+68=0

11x=220

x=220:11

x=20

a) \(\dfrac{25}{37}\times\dfrac{18}{29}+\dfrac{18}{29}\times\dfrac{12}{37}\)

\(=\dfrac{18}{29}\times\left(\dfrac{25}{37}+\dfrac{12}{37}\right)\)

\(=\dfrac{18}{29}\times\dfrac{37}{37}\)

\(=\dfrac{18}{29}\times1\)

\(=\dfrac{18}{29}\)

b) \(\dfrac{31}{85}\times\dfrac{11}{19}+\dfrac{31}{85}\times\dfrac{12}{19}-\dfrac{42}{19}\times\dfrac{31}{85}\)

\(=\dfrac{31}{85}\times\left(\dfrac{11}{19}+\dfrac{12}{19}-\dfrac{42}{19}\right)\)

\(=\dfrac{31}{85}\times\dfrac{-19}{19}\)

\(=\dfrac{31}{85}\times-1\)

\(=-\dfrac{31}{85}\)

c) \(\dfrac{16}{53}:\dfrac{17}{9}-\dfrac{16}{53}:\dfrac{17}{8}\)

\(=\dfrac{16}{53}:\left(\dfrac{9}{17}-\dfrac{8}{17}\right)\)

\(=\dfrac{16}{53}:\dfrac{1}{17}\)

\(=\dfrac{16}{901}\)

c) \(\dfrac{1}{5}\times\dfrac{12}{31}\times\dfrac{4}{3}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\dfrac{12}{31}+\dfrac{19}{31}\times\dfrac{4}{15}\)

\(=\dfrac{4}{15}\times\left(\dfrac{12}{31}+\dfrac{19}{31}\right)\)

\(=\dfrac{4}{15}\times\dfrac{31}{31}\)

\(=\dfrac{4}{15}\times1\)

\(=\dfrac{4}{15}\)

a: =18/29*(25/37+12/37)

=18/29

b: =31/85(11/19+12/19-42/19)

=-31/85

c; =16/53(9/17+8/17)=16/53

d: =4/15(12/31+19/31)=4/15

Tìm số nguyên x, biết:
1) -16 + 23 + x = - 16

7+x=-16

    x=-16-7

    x=-23
2) 2x – 35 = 15

2x=15+35

2x=50

  x=50:2

  x=25
3) 3x + 17 = 12

3x=12-17

3x=-5

  x=-5/3
4) (2x – 5) + 17 = 6

2x-5=6-17

2x-5=-11

2x=-11+5

2x=-6

  x=-6:2

  x=-3
5) 10 – 2(4 – 3x) = -4

2(4-3x)=10-(-4)

2(4-3x)=14

4-3x=14:2

4-3x=7

3x=4-7

3x=-3

  x=-3:3

  x=-1
6) - 12 + 3(-x + 7) = -18

3(-x+7)=-18-(-12)

3(x+7)=-6

x+7=-6:3

x+7=-2

    x=-2-7

    x=-9

tự đi mà làm

x=-14 nha

k mình nhé thanks

[ (-17) - (18 - x) - (-14) ] - (-16) = 17

(-17) - 18 + x + 14 + 16 = 17

-35 + x + 30 = 17

-35 + x = 17 - 30

-35 + x = -47

x = -47 + 35

x = -12

đung 100%