Lớp 6 rồi mà gà quá :v

Ta có:

10+20+30=(120:(x-6)+24)

=>(120:(x-6)+24)=60

=> 120:(x-6)=36

=> x-6=10/3

=> x=28/3

Ta có :

10 + 20 = 30 = [ 120 : ( x - 6 ) + 24 ]

Suy ra [ 120 : ( x - 6 ) + 24 ] = 60

Suy ra 120 : ( x - 6 ) = 36

Suy ra x - 6 = 10/3

Suy ra x = 28/3

a) x = 34             

b) x= 5                

c) x = 35              

d) x = 0

e) x = 410            

f) x= 170

mk lm cách khác, bn tham khảo nhé

     \(P\left(x\right)=\left(x+5\right)\left(x+10\right)\left(x+15\right)\left(x+20\right)+2016\)

\(=\left(x^2+25x+100\right)\left(x^2+25x+150\right)+2016\)

Đặt   \(x^2+25x+125=a\)  ta có:

         \(P\left(x\right)=\left(a-25\right)\left(a+25\right)+2016\)

                     \(=a^2-625+2016\)

                     \(=a^2-25+1416\)

                     \(=\left(a-5\right)\left(a+5\right)+1416\)

Thay trở lại ta được:   \(P\left(x\right)=\left(x^2+25x+120\right)\left(x^2+25x+130\right)+1416\)

Ta thấy      \(\left(x^2+25x+120\right)\left(x^2+25x+130\right)\) \(⋮\) \(x^2+25x+120\)

suy ra         \(P\left(x\right)\) chia  cho     \(x^2+25x+120\) dư   \(1416\)

Ta có : P_(x) = (x + 5)(x + 20)(x +15)(x + 10)

=> P(x) = (x² + 25x + 100)(x² + 25x + 150)

=> P(x) = (x² + 25x + 120)(x² + 25x + 150) - 20(x² + 25x + 150)

=> P(x) = (x² + 25x + 120)(x² + 25x + 150) - 20(x² + 25x + 120) - 20.30 

=> P(x) = (x² + 25x + 120)(x² + 25x + 150 - 20) - 600

Vì   (x² + 25x + 120)(x² + 25x + 150 - 20)  chia hết cho (x² + 25x + 120) 

Nên : Số dư là : 600

x+6.20=120.10

x+120=1200

x=1200-120

x=1080

x + 6 x 20 = 120 x 10

x + 120 = 1 200

x = 1 200 - 120

x = 1 080

a) \(\left(2x-18\right):\left(-10\right)-34=2\)

\(\Rightarrow\left(2x-18\right):\left(-10\right)=2+34\)

\(\Rightarrow\left(2x-18\right):\left(-10\right)=36\)

\(\Rightarrow2x-18=36\cdot\left(-10\right)\)

\(\Rightarrow2x-18=-360\)

\(\Rightarrow2x=-360+18\)

\(\Rightarrow2x=-342\)

\(\Rightarrow x=-342:2\)

\(\Rightarrow x=-171\) 

b) \(120:\left(5x+20\right)-45=75\)

\(\Rightarrow120:\left(5x+20\right)=75+45\)

\(\Rightarrow120:\left(5x+20\right)=120\)

\(\Rightarrow5x+20=120:120\)

\(\Rightarrow5x+20=1\)

\(\Rightarrow5x=1-20\)

\(\Rightarrow5x=-19\)

\(\Rightarrow x=-\dfrac{19}{5}\)

\(2\left(x-5\right)+10=20\)

\(2x-10+10=20\)

\(2x=20\)

\(x=10\)

\(\left(3x+1\right)-17=5\)

\(3x+1-17=5\)

\(3x-16=5\)

\(3x=21\)

\(x=\frac{21}{3}=7\)

\(\left(10x+120\right)-138=262\)

\(10x+120-138=262\)

\(10x-18=262\)

\(10x=280\)

\(x=28\)

\(4\left(x+1\right)-12=8\)

\(4x+4-12=8\)

\(4x-8=8\)

\(4x=16\)

\(x=4\)

2.(x-5)+10 = 20

2.(x-5) = 20 - 10

2.(x-5) = 10

x-5 = 10 : 2

x-5 = 5

x = 5 + 5

x = 10

(3x+1)-17 = 5

3x+1 = 5 + 17

3x+1 = 22

3x = 22 - 1

3x = 21

x = 21 : 3

x = 7

(10x+120)-138 = 262

10x+120 = 262 + 138

10x+120 = 400

10x = 400-120

10x = 280

x = 280 : 10

x = 28

4.(x+1)-12 = 8

4.(x+1) = 8 + 12

4.(x+1) = 20

x+1 = 20 : 4

x+1 = 5

x = 5 - 1

x = 4

\(2x+2\frac{1}{3}=\frac{1}{2}:\frac{3}{2}\)

\(2x+\frac{7}{3}=\frac{1}{3}\)

\(2x=\frac{1}{3}-\frac{7}{3}\)

\(2x=-2\)

x = (-2) : 2

x = -1

(x-14)-20=5

=> x-14 = 25

=> x = 39

Các dạng toán như này lớp 6 ai cũng làm được cả * lười vừa thôi*

( x - 14 ) - 20 = 5

 x - 14 = 5 + 20

 x - 14 = 25

 x = 25 + 14

 x = 39

128 + ( 202 - x ) = 330

           [ 202 - x ] = 330 - 128

             202 - x = 202

                      x = 202 - 202

                      x = 0

( x - 120 ) x 9 = 450

[ x - 120 ] = 450 : 9

 x - 120 = 50

 x = 50 + 120

 x = 170

x - 320 : 32 = 25 x 16

x - 320 : 32 = 400

x - 320 = 400 x 32

x - 320 = 12800

x = 12800 + 320

x = 13120

25 - ( 2x +10 ) = 5

        [ 2x + 10] = 25 - 5

          2x + 10 = 20

          2x = 20 - 10

          2x = 10

            x = 10 : 2

            x = 5

315 - ( 135 - x ) = 215

          [ 135 - x ] = 315 - 215

          [ 135 - x ] = 100

                      x = 135 - 100

                      x = 35

x : 2 + 21 : 3 = 37

x : 2 + 21 = 37 x 3

x : 2 + 21 = 111

x : 2 = 111 - 21

x : 2 = 90

x = 90 x 2

x = 180

4 x ( x + 100 ) = 800

      [ x + 100 ] = 800 : 4

      [ x + 100 ] = 200

       x = 200 - 100

       x = 100

504 : ( 16 - 5x ) = 72

          [ 16 - 5x ] = 504 : 72

           [ 16 - 5x ] = 7

                     5x = 16 - 7

                     5x = 9

                       x = \(\dfrac{9}{5}\)

( x - 5 ) : 7 + 3 = 20

[ x - 5 ] : 7 = 20 - 3

[ x - 5 ] : 7 = 17

[ x - 5 ] = 17 x 7

 x - 5 = 119

 x = 119 + 5

 x = 124

a) 120 - 20 : x = 110

20:x= 120 - 110

20:x= 10

x= 20:10=2

b) 213 - ( x - 13 ) = 1442 : 14

213 - (x-13)=103

x-13= 213 - 103

x-13=110

x=110+13

x=123

c) 2550 : [ 120 - ( x - 5 ) ] = 25

120 - (x-5) = 2550:25

120 - (x-5)=102

x-5 = 120 - 102

x-5= 18

x=18+5

x=23

a,120-20:X=110

20:X=120-110

20:X=10

     X=20:10

     X=2