a) (-12) . (x - 14) + 7 . (3 - x) = 12.15

=> -12x + 168 + 21 - 7x = 180

=> -19x = -9

=> x = \(\frac{9}{19}\)

b) (2x - 8) . ( y - 2) = 0

=> \(\left\{\begin{matrix}2x-8=0\\y-2=0\end{matrix}\right.\Rightarrow\left\{\begin{matrix}x=4\\y=2\end{matrix}\right.\)

c) x^2 - 75 = (-50)

=> \(x^2\)=25

=> \(\left[\begin{matrix}x=5\\x=-5\end{matrix}\right.\)

d) (2x - 5)^2 - 1 = 0

=> ( 2x - 5 ) ^2 = 1

=> \(\left[\begin{matrix}2x-5=1\\2x-5=-1\end{matrix}\right.\)

=>\(\left[\begin{matrix}x=3\\x=2\end{matrix}\right.\)

e) (3y + 6)^3 + 27 = 0

=> \(\left(3y+6\right)^3=-27\)

=> 3y + 6 = -3

=> y = -3

Mk cần gấp để nộp ạ

( 2 x y + 2/15 ) x 3 = 4/5

( 2 x y + 2/15 )      = 4/5 : 3 

( 2 x y + 2/15 )      =   4/15

 2 x y                    = 4/15 - 2/15 

2 x y                     =     2/15

     y                      =     2/15 :2 

   y                          =    1/15

(2 x y + 2/15) x 3 = 4/5 

2 x y + 2/15) = 4/5 : 3 

2 x y + 2/15 = 4/15 

2 x y = 4/15 - 2/15 

2 x y = 2/15 

y = 2/15 : 2 

y = 1/15 

7/9 x (2 - 1/3 x y) = 14/15 

(2 - 1/3 x y) = 14/15 : 7/9 

(2 - 1/3 x y) = 6/5 

2 - y = 6/5 x 1/3 

2 - y = 2/5 

y = 2/5 + 2 

y = 12/5 

4/21 + 5 x y - 8/7 = 1/3 

4/21 + 5 x y = 1/3 + 8/7 

4/21 + 5 x y = 31/21 

5 x y = 31/21 - 4/21 

5 x y = 9/7 

y = 9/7 : 5 

y = 9/35 

7/12 x y - 3/12 x y = 5 

y x (7/12 - 3/12) = 5 

y x 1/3 = 5 

y = 5 : 1/3 

y = 15 

a) y : 4/11 x 3/5 = 27/4

y : 4/11 = 27/4 : 3/5

y : 4/11 = 45/4

y = 45/4 x 4/11

y = 45/11

b) y + 7/2 - 5/9 = 14/3

y + 7/2 = 14/3 + 5/9

y + 7/2 = 47/9

y = 47/9 - 7/2

y = 31/18

a) y : 4/11 x 3/5 = 27/4

y : 4/11 = 27/4 : 3/5

y : 4/11 = 45/4

y = 45/4 x 4/11

y = 45/11
b) y + 7/2 - 5/9 = 14/3

y + 7/2 = 14/3 + 5/9

y + 7/2 = 47/9

y = 47/9 - 7/2

y = 31/18

\(\)a) \(y\) : \(\dfrac{4}{11}\) x \(\dfrac{3}{5}\) \(=\) \(\dfrac{27}{4}\)                   b) \(y\) \(+\) \(\dfrac{7}{2}\) \(-\) \(\dfrac{5}{9}\) \(=\) \(\dfrac{14}{3}\)

    \(y\) : \(\dfrac{4}{11}\)        \(=\) \(\dfrac{27}{4}:\dfrac{3}{5}\)                 \(y\) \(+\) \(\dfrac{7}{2}\)          \(=\) \(\dfrac{14}{3}\) \(+\) \(\dfrac{5}{9}\) 

    \(y\) : \(\dfrac{4}{11}\)        \(=\) \(\dfrac{45}{4}\)                       \(y\) \(+\) \(\dfrac{7}{2}\)           \(=\) \(\dfrac{47}{9}\)

    \(y\)                \(=\) \(\dfrac{45}{4}\) x \(\dfrac{4}{11}\)              \(y\)                    \(=\) \(\dfrac{47}{9}-\dfrac{7}{2}\)

    \(y\)                \(=\) \(\dfrac{45}{11}\)                      \(y\)                     \(=\) \(\dfrac{31}{18}\)

a, \(x+y+z-x-y+z=2z\)

Thay z=-10 Thì \(2z=-20\)

b, \(a-b-c+a+b=2a-c=2\cdot\left(-12\right)-\left(-27\right)=3\)

hay giai giup minh

Lời giải:
a. $(-12)-x=(-12)-(-28)=-12+28=28-12=16$

b. $(23+x)-(56-x)=(23+7)-(56-7)=30-49=-19$

c. $25-x-(29+y-8)=25-13 -(29+11-8)=12-32=-20$

Bài 9:

Ta có: \(\dfrac{12}{-6}=\dfrac{x}{5}=\dfrac{-y}{3}=\dfrac{z}{-17}=\dfrac{-t}{-9}\)

\(\Leftrightarrow\dfrac{x}{5}=\dfrac{-y}{3}=\dfrac{-z}{17}=\dfrac{t}{9}=-2\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{x}{5}=-2\\\dfrac{-y}{3}=-2\\\dfrac{-z}{17}=-2\\\dfrac{t}{9}=-2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-10\\-y=-6\\-z=-34\\t=-18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-10\\y=6\\z=34\\t=-18\end{matrix}\right.\)

Vậy: (x,y,z,t)=(-10;6;34;-18)

Bài 11:

Ta có: \(\dfrac{-7}{6}=\dfrac{x}{18}=\dfrac{-98}{y}=\dfrac{-14}{z}=\dfrac{t}{102}=\dfrac{u}{-78}\)

\(\Leftrightarrow\dfrac{x}{18}=\dfrac{-98}{y}=\dfrac{-14}{z}=\dfrac{t}{102}=\dfrac{u}{-78}=\dfrac{-7}{6}\)

Ta có: \(\dfrac{x}{18}=\dfrac{-7}{6}\)

\(\Leftrightarrow x=\dfrac{18\cdot\left(-7\right)}{6}=-21\)

Ta có: \(\dfrac{-98}{y}=\dfrac{-7}{6}\)

\(\Leftrightarrow y=\dfrac{-98\cdot6}{-7}=84\)

Ta có: \(\dfrac{-14}{z}=\dfrac{-7}{6}\)

\(\Leftrightarrow z=\dfrac{-14\cdot6}{-7}=12\)

Ta có: \(\dfrac{u}{-78}=\dfrac{-7}{6}\)

\(\Leftrightarrow u=\dfrac{-78\cdot\left(-7\right)}{6}=\dfrac{78\cdot7}{6}=91\)

Ta có: \(\dfrac{t}{102}=\dfrac{-7}{6}\)

\(\Leftrightarrow t=\dfrac{-7\cdot102}{6}=-7\cdot17=-119\)

Vậy: (x,y,z,t,u)=(-21;84;12;-119;91)

Nguyễn Lê Phước Thịnh giải giùm mk bài 10 đc ko ạ