a) x=-2

b)x=7

c)x=11 hay -11

d)không có giá trị

e)x=85

f)x=-55

g)x=0

****

a) 4x - 15 = -75 -x

   4x+x = -75 + 15

   5x = 60

     x= 60: 5

  => x= 12

b) 3| x-7| = 21

      |x-7|= 21:3

      |x-7|=7

  => x-7 =7 hoặc x-7=-7

 +) x-7=7

     x=7+7=14

  +) x-7=-7

      x= -7+7=0

=> x=14 hoặc x=0

c) Áp dụng t/c phân số bằng nhau 

=> x= \(\frac{-3.\left(-2\right)}{6}\)=\(\frac{6}{6}\)=1

Thay x=1 => y= \(\frac{\left(-2\right).\left(-18\right)}{1}\)=\(\frac{36}{1}\)=36

Thay y =36 => z=\(\frac{\left(-18\right).24}{36}\)=\(\frac{-432}{36}\)=-12

vậy (x,y,z)= (1;36;-12)

(câu d dài quá vs lại cx dễ nên bn tự lm nha mk chỉ giúp đến đây thôi)

a) \(5\left(x-7\right)=0\)

\(\Rightarrow x-7=0\)

\(\Rightarrow x=7\)

b) \(25\left(x-4\right)=0\)

\(\Rightarrow x-4=0\)

\(\Rightarrow x=4\)

c) \(\left(34-2x\right)\left(2x-6\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}34-2x=0\\2x-6=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}2x=34\\2x=6\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=17\\x=3\end{matrix}\right.\)

d) \(\left(2019-x\right)\left(3x-12\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}2019-x=0\\3x-12=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2019\\3x=12\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2019\\x=\dfrac{12}{3}=4\end{matrix}\right.\)

e) \(57\left(9x-27\right)=0\)

\(\Rightarrow9x-27=0\)

\(\Rightarrow9\left(x-3\right)=0\)

\(\Rightarrow x-3=0\)

\(\Rightarrow x=3\)

a) 5.(x-7)=0⇔x-7=0⇔x=7

b) 25(x-4)=0⇔x-4=0⇔x=4

c) (34-2x).(2x-6)=0

⇔ 34-2x=0 hoặc 2x-6=0

⇔2x=34 hoặc 2x=6

⇔ x=17 hoặc x=3

d) (2019-x).(3x-12)=0

⇔ 2019-x=0 hoặc 3x-12=0

⇔ x=2019 hoặc x=4

e) 57.(9x-27)=0

⇔ 9x-27=0

⇔ x=3

f) 25+(15-x)=30

⇔ 15-x=5

⇔ x=10

g) 43-(24-x)=20

⇔ 24-x=23

⇔ x=1

h) 2.(x-5)-17=25

⇔ 2(x-5)=42

⇔x-5=21

⇔ x=26

i) 3(x+7)-15=27

⇔ 3(x+7)=42

⇔ x+7=14

⇔ x=7

j) 15+4(x-2)=95

⇔ 4(x-2)=80

⇔ x-2=20

⇔ x=22

k) 20-(x+14)=5

⇔ x+14=15

⇔ x=1

l) 14+3(5-x)=27

⇔ 3(5-x)=13

⇔ 5-x=13/3

⇔ x=5-13/3

⇔ x=2/3

a) 4x- 15 = -75 - x

=> 4x + x = -75 + 15

=> 5x = -60

=> x = -60 : 5

=> x = -12

b) 3(x  - 7) = 21

=> x - 7 = 21 : 3

=> x - 7 = 7

=> x = 7 + 7

=> x = 14

c) \(-\frac{3}{6}=\frac{x}{-2}=\frac{-18}{y}=\frac{-z}{24}\)

Ta có: +) \(-\frac{3}{6}=\frac{x}{-2}\) => \(\frac{1}{-2}=\frac{x}{-2}\) => x = 1

+) \(\frac{-3}{6}=\frac{-18}{y}\) => \(\frac{-18}{36}=\frac{-18}{y}\) => y = 36

+) \(-\frac{3}{6}=\frac{-z}{24}\) = > \(\frac{-12}{24}=\frac{-z}{24}\) => -z = -12 => z = 12

d) \(-\frac{8}{3}+\frac{-1}{4}< x< \frac{-2}{7}+\frac{-5}{7}\)

=> \(\frac{-32}{12}-\frac{3}{12}< x< \frac{-2-5}{7}\)

=> \(\frac{-35}{12}< x< -1\)

=> x = -2 (x \(\in\)Z)

a) 4x - 15 = -75 - x

4x + x = -75 + 15

5x  = -60

=> x = -60 : 5 = -12

a)

− 12 . x = − 15 . − 4 − 12 − 12 . x = 60 − 12 − 12 . x = 48                x = 48 : − 12                x = − 4

b) 

− 9 . x + 3 = − 2 . − 7 + 16 − 9 . x + 3 = 14 + 16 − 9 . x + 3 = 30 − 9 . x           = 30 − 3 − 9 . x           = 27              x           = 27 : − 9              x           = − 3

c)

− 12 . x − 34 = 2 − 12 . x               = 2 + 34 − 12 . x               = 36                x                = 36 : − 12                x                = − 3

a)

− 12 . x = − 15 . − 4 − 12 − 12 . x = 60 − 12 − 12 . x = 48                x = 48 : − 12                x = − 4

b)

− 9 . x + 3 = − 2 . − 7 + 16 − 9 . x + 3 = 14 + 16 − 9 . x + 3 = 30 − 9 . x           = 30 − 3 − 9 . x           = 27              x           = 27 : − 9              x           = − 3

c) 

− 12 . x − 34 = 2 − 12 . x               = 2 + 34 − 12 . x               = 36                x                = 36 : − 12                x                = − 3

a) (71+x)-(-24-x)+(-35-x)=0                                    b)x-34-[(15+x)-(23-x)]=0

     71+x+24+x+-35-x    =0                                      x-34-15-x-23+x       =0

      (x+x-x)+(71+24-35) =0                                     (x-x+x)+(-34-15-23)  =0

              x+60             =0                                              x+-72             =0

              x                   =0-60                                         x                    =0-(-72)

              x                  = -60                                           x                    = 72

BAI 1 ; 

Bài 2: 

a, \(\dfrac{5}{23}\) \(\times\) \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) \(\times\) \(\dfrac{9}{26}\) 

= \(\dfrac{5}{23}\) \(\times\) ( \(\dfrac{17}{26}\) + \(\dfrac{9}{26}\))

= \(\dfrac{5}{23}\) \(\times\) \(\dfrac{26}{26}\)

= \(\dfrac{5}{23}\) 

b, \(\dfrac{3}{4}\) \(\times\) \(\dfrac{7}{9}\) + \(\dfrac{7}{4}\)  \(\times\) \(\dfrac{3}{9}\)

= \(\dfrac{7}{12}\) + \(\dfrac{7}{12}\)

= \(\dfrac{14}{12}\)

= \(\dfrac{7}{6}\)

1,a) \(\dfrac{17}{20}=\dfrac{51}{60};\dfrac{13}{15}=\dfrac{52}{60}\)