B2:tìm x biết

1)x+18=6-2x

<=> 3x=-12

<=> x= -4

 2)17-x=7-6x

<=>5x=-10

<=>x=-2            

3)x+15=20-4x  

<=>5x=5

<=>x=1

4)7x-4=20+3x                

<=> 4x=24

<=>x=6

5)-12+x=5x-20    

<=>4x=8

<=>x=2

6)4x-18=x+27

<=>3x=45

<=>x=9

7) 2.(x-5)-3.(x+7)=14

<=>2x-10-3x-21=14

<=>-x=14+10+21=45

<=>x=-45

8)5.(x-6)-2.(x+3)=12

<=>5x-30-2x-6=12

<=>3x=48

<=>x=12

9)-7.(5-x)-2.(x-10)=15

<=>-35+7x-2x+20=15

<=>5x=30

<=>x=6

10)3. ( x - 4 ) - ( 8 - x )=12

<=>3x-12-8+x=12

<=>4x=32

<=>x=8

11)4.(x-5)-(x+7)=-19

<=>4x-20-x-7=-19

<=>3x=8

<=>x=8/3

 12)7.(x-3)-5.(3-x)=11x-5

<=>7x-21-15+5x=11x-5

<=>x=31

b1:bỏ ngoặc rồi tinh hợp lí

1) -( -66)+34+(-73)-27+99=66+34-73-27+99 =100-100+99=99

2)54-(45-30+54)-30+5=54-45+30-54-30+5=-45+5=-40     

3)42-56+33-(33-56+42)=42-56+33-33+56-42=0

4)50-(47+50-18)+(47-18)=50-47-50+18+47-18=0      

5) |25-24-10|-(28-30+4)=9-28+30-4=39-32=7

6)-(-73)+(44-94+27)+94=73+44-94+27+94=100+44=144

7) (-33+180-75)-(180+25)=-33+180-75-180-25=-100-33=-133

8)120-(-92+120-18)-92=120+92-120+18=108

b1:bỏ ngoặc rồi tinh hợp lí 

1) -( -66)+34+(-73)-27+99=66+34-73-27+99 =100-100+99=99 

2)54-(45-30+54)-30+5=54-45+30-54-30+5=-45+5=-40 

3)42-56+33-(33-56+42)=42-56+33-33+56-42=0

4)50-(47+50-18)+(47-18)=50-47-50+18+47-18=0 

5) |25-24-10|-(28-30+4)=9-28+30-4=39-32=7 

6)-(-73)+(44-94+27)+94=73+44-94+27+94=100+44=144 

7) (-33+180-75)-(180+25)=-33+180-75-180-25=-100-33=-133 

8)120-(-92+120-18)-92=120+92-120+18=108

47. (23 + 50)- 23. ( 47+50 )

= 47. 23+ 47. 50- 23. 47 - 23. 50

=47. 50 - 23. 50

= 50 .( 47 -23)

=50. 24 = 1200

(-33 ). (-5) - 33 . 4 + 33

= 33 ( 5 - 4 + 1)

=33 . 2 = 66

giup minh voi 

a) 2x -18 = 10

    =>2x = 28

    => x = 14

b) 3x + 26 = 5

=> 3x = -21

=> x = -7

Ai làm cả 2 bài mình tích

Bài 1 :

a, 25 + (-42) = - ( 42 - 25 ) = - 17

b, (-17) + 5 + 8 + 17 + (-3 )

= [ (-17) + 17 ] + [ ( 5 + 8 ) + (-3) ]

= 0 + 10

= 10

c, 25. 2² - ( 15-18 ) + ( 12 - 19 + 10 )

= 25 . 4 - (-3) + 3

= 100 - [ (-3) + 3 ]

= 100 - 0

= 100

d, 120 - 35 + 29 - 242

= 85 + 29 - 242

= 114 - 242

= -128

38x2=76

26x4=104

42x5=210

77x3=231

54x6=324

48x3=144

38x2=76 ;77x3=231 ;26x4=104  ;54x6=324 ;42x5=210 ;48x3=144

38 x 2 = 76

26 x 4 = 104

42 x 5=210

77 x 3 = 231

54 x 6 = 324

48 x 3 =144

                             HOK TỐT -_-

a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)

\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)

=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)

b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)

Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)

c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)

\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)

=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)

d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)

\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6

=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)

a) 54 + ( 218 - x ) = 735

218 - x = 735 - 34

218 - x = 701

        x = 218 - 701

        x = -483

b) 96 - 3 ( x + 1 ) = 42

3 ( x + 1 ) = 96 - 42

3 ( x + 1 ) = 54

x + 1 = 54 : 3

x + 1 = 18

      x = 18 - 1

      x = 17

c) 5 ( x + 35 ) 515

x + 35 = 515 : 5

x + 35 = 103

       x  = 103 - 35

       x  = 68

d) 12x - 33 = 3² . 3²

12x - 33 = 9.9

12x - 33 = 81

12x = 81 + 33

12x = 114

    x = 114 : 12

    x = 9,5

a) 54+(218-x)=735

          218-x=681

                x=-463

b) 96-3(x+1)=42

         3(x+1)=54

           x+1=18

           x=17

c) 5(x+35)=515

      x+35=103

       x=68

d) 12x-33=3^2.2^2

     12x-33=81

      12x = 114

          x=9,5

Nhấn đúng cho mk nha!!!!!!!!

ồ

dễ nhỉ

thế cũng hỏi sao

k mk nha

k mk mk k lại

Ai lm hộ mk nha

Nhiều quá bạn ơi

1.\(x-43=\left(35-x\right)-48\)

\(\Rightarrow x-43=35-x-48\)

\(\Rightarrow2x=35+43-48\)

\(\Rightarrow2x=30\)

\(\Rightarrow x=15\)

2.\(305-x+14=48+\left(x-23\right)\)

\(\Rightarrow305-x+14=48+x-23\)

\(\Rightarrow305+14=48+x+x-23\)

\(\Rightarrow2x+25=319\)

\(\Rightarrow2x=294\)

\(\Rightarrow x=147\)

3.\(-\left(x-6+85\right)=\left(x+51\right)-54\)

\(\Rightarrow-x+6-85=x+51-54\)

\(\Rightarrow6-85=x+x+51-54\)

\(\Rightarrow2x-3=-79\)

\(\Rightarrow2x=-76\)

\(\Rightarrow x=-38\)

4.\(-\left(35-x\right)-\left(37-x\right)=33-x\)

\(\Rightarrow-35+x-37+x=33-x\)

\(\Rightarrow2x-72=33-x\)

\(\Rightarrow3x=105\)

\(\Rightarrow x=35\)

5.\(13-\left|x\right|=\left|-4\right|\)

\(\Rightarrow13-\left|x\right|=4\)

\(\Leftrightarrow\left[{}\begin{matrix}13-x=4\\13+x=4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=9\\x=-9\end{matrix}\right.\)