a/x=0

b/90

c/121

d/15

e/15

a) 0

b)  x - 15 =75

x=15+75=

x=90

c)  ( x - 7 ) = 114+0

      x - 7 = 114

x=114+7

x=121

d)  ( x - 15 ) = 0:2015

       x - 15 =0

  x=15+0

x=15

e)( x - 15 ) =0:13

x - 15 =0

x=15+0

x+15

a. 25 . x = x

x = 0

b. ( x - 15 ) - 75 = 0

x - 15 = 0 + 75 

x - 15 = 75

x = 75 + 15

x = 90

c. 114 - ( x - 7 ) = 0

x - 7 = 114 - 0

x - 7 = 114

x = 114 + 7

x = 121

d. 2015 x ( x - 15 ) = 0

x - 15 = 0 : 2015

x - 15 = 0

x = 0 + 15

x = 15

e. ( x - 15 ) x 13 = 0

x - 15 = 0 : 14

x - 15 = 0

x = 0 + 15

x = 15 

a) \(\left(x-15\right)-75=0\\ \Leftrightarrow x-15=75\\ \Leftrightarrow x=90\)

b) \(575-\left(6x+70\right)=445\\ \Leftrightarrow6x+70=130\\ \Leftrightarrow6x=60\\ \Leftrightarrow x=10\)

c) \(x-105:21=15\\ \Leftrightarrow x-5=15\\ \Leftrightarrow x=20\)

d) \(\left(x-105\right):21=15\\ \Leftrightarrow x-105=315\\ \Leftrightarrow x=420\)

a) ( x - 15 )   - 75  = 0

x -15 = 75 + 0

x - 15 = 75

x= 75 + 15

x = 90    

b) 575- (6x +70) =445   

6x + 70 = 575 - 545 

6x + 70 = 130

6x = 130 - 70 

6x  = 60

x = 60 : 6

x = 10

c) x –105 : 21 =15     

x –105  = 15 x 21

x -105 = 315

x = 315 + 105

x = 420

d) (x - 105) :21 = 15

x - 105 = 21

x = 105 + 21 

x = 126

a) (x - 5) - 75 = 0

     x - 5         = 75 + 0

     x - 5         = 75

     x              = 75 + 5

    x               = 80

b) 575 - (6x + 70) = 445

               6x + 70  = 575 - 445

               6x + 70  =  130

               6x          =  130 - 70

               6x          =    60

                 x          =    60 : 6

                 x          =     10

c) x - 105 : 21 = 15

   x -     5         = 15

   x                  = 15 + 5

   x                  =  20

d) (x - 105) : 21 = 15

    x - 105        =  15 x 21

    x -150         = 135

    x                 = 135 + 150

    x                 =    285 

\(\left(x-15\right)-75=0\)

\(x-15=0+75\)

\(x-15=75\)

\(x=75+15\)

\(x=90\)

Học tốt

\(\left(x-15\right)-75=0\)

\(x-15=75\)

\(x=75+15\)

\(x=90\)

Vậy : x = 90

x-15=0+75

x-15=75

x     =75+15

x     =90

a) \(\left(2+x\right):5=6\)

\(2+x=6\times5\)

\(2+x=30\)

\(x=30-2\)

\(x=28\)

b) \(\left(3\times x+15\right)-75=0\)

\(3\times x+15=0+75\)

\(3\times x+15=75\)

\(3\times x=75-15\)

\(3\times x=60\)

\(x=60:3\)

\(x=20\)

Chỉ áp dụng cho những bn lớp 8-9 :D

\(a,\left(x-2\right)\left(2013-3x\right)=0\)

\(< =>2013x-3x^2-4026+6x=0\)

\(< =>-3x^2+2019x-4026=0\)

Ta có : \(\Delta=2019^2-4.\left(-3\right)\left(-4026\right)=4076361-48312=4028049\)

\(< =>\sqrt{\Delta}=2007\)

Vì delta > 0 nên pt có 2 nghiệm phân biệt

\(x_1=\frac{-2019+2007}{-6}=\frac{-12}{-6}=2\)

\(x_2=\frac{-2019-2007}{-6}=\frac{-4026}{-6}=671\)

Vậy ...

bạn có thể làm bằng kiến thức lớp 6 được không

1) (x -2).(2013 - 3x) = 0

\(\Rightarrow\hept{\begin{cases}x-2=0\\2013-3x=0\end{cases}\Rightarrow\hept{\begin{cases}x=2\\-3x=-2013\end{cases}\Rightarrow}\hept{\begin{cases}x=2\\x=671\end{cases}}}\)

2, 4x -15 = -75 - x

\(\Leftrightarrow4x+x=-75+15\)

\(\Leftrightarrow5x=-60\)

\(\Leftrightarrow x=-12\)

a,(x-15)-75=0

x-15         =75

x              =75+15

x             =90

b,72-(6.x+5)=55

6.x+5=72-55

6.x+5=17

6.x=17-5

6.x=12

x=12:6

x=2

c,575-(6.x+70)=445

6.x+70=575-445

6.x+70=130

6.x=130-70

6.x=60

x=60:6

x=10

d,(x-34).15=0

x-34=0

x=34

e,15+(18-x)=26

18-x=26-15

18-x=11

x=18-11

x=7

g,(x-5):16=2

x-5=2.16

x-5=32

x=32+5

x=37

(3x - 15) - 75 = 0

3x - 15 = 75

3x = 75 + 15

3x = 90

x = 90 : 3

x = 30

-------------------

3²ˣ⁻¹ = 27

3²ˣ⁻¹ = 3³

2x - 1 = 3

2x = 4

x = 2

a) \(\left(x-2018\right)\cdot3=0\)

\(\Leftrightarrow x-2018=0\)

\(\Leftrightarrow x=2018\)

b) \(25\left(x-8\right)=0\)

\(\Leftrightarrow x-8=0\)

\(\Leftrightarrow x=8\)

c) \(25+\left(15+x\right)=75\)

\(\Leftrightarrow15+x=50\)

\(\Leftrightarrow x=35\)

a) x=2018

b)x=8

c)x=35

Bài 2:

a, (x-2018).3=0

<=> x-2018=0

<=>x=0+2018

<=>x=2018

Vậy x=2018

b, 25(x-8)=0

<=> x-8=0

<=> x=0+8

<=>x=8

Vậy x=8

c, 25+(15+x)=75

<=> 25+15+x=75

<=> 40+x=75

<=>x=75-40

<=>x=35

Vậy x=35

a: A={71;72;73;74}

b: B={41;43;45;47;49}

c: C={0}

d: D=R

A = ( 71,72,73,74 )

B = ( 41,43,45,47,49 )

C = ( 0)

D = ( 1,2,3,4,5,6,7,......., N )