\(\text{a/96-3(x+1)=42}\)

\(3\left(x+1\right)=54\)

\(x+1=54:3\)

\(x+1=18\)

\(\Rightarrow x=17\)

\(\text{b/2.x-18=20}\)

\(2x=38\)

\(x=38:2\)

\(x=19\)

\(\text{c/134-5.(x+4)=34}\)

\(5\left(x+4\right)=100\)

\(x+4=100:5\)

\(x+4=20\)

\(\Rightarrow x=16\)

học tốt

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

3(x+1)=96-42

3(x+1)=54

x+1=54:3

x+1=18

x=18-1

Vậy x=17

b) 2x-18=20

2x=20+18

2x=38

x=38:2

x=19

Vậy x=19.

c) 134-5(x+4)=34

5(x+4)=134-34

5(x+4)=100

x+4=100:5

x+4=20

x=20-4

x=16

Vậy x=16.

a) 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

Vậy x=17

b)2.x-18=20

   2.x     =20+18

   2.x     =38

      x     =38:2

      x     =19

Vậy x=19

c)134-5.(x+4)=34

          5.(x+4)=134-34

          5.(x+4)=100

              x+4 =100:5

              x+4 =20

                  x =20-4

                  x =16

Vậy x=16
 

a) 5.(x-20) = 35

(x-20) = 35:5

x-20 = 7

x = 27

b) (x+125) -301 = 56

x+125 -301 = 56

x - 176 = 56

x = 56 +176

x= 232

c) 215 + (x-21):2 = 235

(x-21):2 = 235 - 215

(x-21):2 = 20

x-21 = 20 .2

x-21 = 40

x = 61

d) (x:23 +45) .67 = 8911

(x:23 +45) = 8911 : 67

x:23+45 = 133

x:23 = 133-45

x:23 = 88

x = 88.23

x = 2024

a) 5.(x - 20) = 35

⇒ x - 20 = 35 : 5

⇒ x - 20 = 7

⇒ x = 7 + 20

⇒ x = 27

b) (x + 125) - 301 = 56

⇒ x + 125 = 56 + 301

⇒ x + 125 = 357

⇒ x = 357 - 125

⇒ x = 232

c) 215 + (x - 21) : 2 = 235

⇒ (x - 21) : 2 = 235 - 215

⇒ (x - 21) : 2 = 20

⇒ x - 21 = 20 x 2 

⇒ x - 21 = 40

⇒ x = 21 + 40

⇒ x = 61

d) (x : 23 + 45).67 = 8911

⇒ x : 23 + 45 = 8911 : 67

⇒ x : 23 + 45 = 133

⇒ x : 23 = 133 - 45

⇒ x : 23 = 88

⇒ x = 88 x 23

⇒ x = 2024

a) \(5.\left(x-20\right)=35\)

\(x-20=35:5\)

\(x-20=7\)

\(x=7+20\Rightarrow x=27\)

b) \(\left(x+125\right)-301=56\)

\(x+125=357\)

\(x=357-125\Rightarrow x=232\)

c) \(215+\left(x-21\right):2=235\)

\(\left(x-21\right):2=20\)

\(x-21=40\Rightarrow x=40+21\Rightarrow x=61\)

d) \(\left(x:23+45\right).67=8911\)

\(x:23+45=133\)

\(x:23=88\Rightarrow x=88.23\Rightarrow x=2024\)

A. 234 x 1257 – 234 x 257

B. 135 x ( 80 + 20 )

Lời giải chi tiết:

+AHƯUẺ6T89U0I-O=ỠNTFIGO8;.,DLDYHỤ890L,SLRT7DFGUYI0-L, G.UIO.;UI...............................................................................................................................................................chó

A. 234 x ( 1257 – 257 )   =  234 x 1257 - 234 x 257

B. 135 x 80 + 20 x 135    =   135 x ( 80 + 20 )

a)\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+x=\frac{3}{5}\)

\(\Rightarrow\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+x=\frac{3}{5}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}+x=\frac{3}{5}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{10}+x=\frac{3}{5}\)

\(\Rightarrow\frac{2}{5}+x=\frac{3}{5}\)

\(\Rightarrow x=\frac{3}{5}-\frac{2}{5}=\frac{1}{5}\)

b)\(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{13.15}+x=\frac{1}{3}\)

\(\Rightarrow\frac{2}{3}-\frac{2}{5}+\frac{2}{5}-\frac{2}{7}+...+\frac{2}{13}-\frac{2}{15}+x=\frac{1}{3}\)

\(\Rightarrow\frac{2}{3}-\frac{2}{15}+x=\frac{1}{3}\)

\(\Rightarrow\frac{8}{15}+x=\frac{1}{3}\)

\(\Rightarrow x=\frac{1}{3}-\frac{8}{15}=-\frac{1}{5}\)

c)\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{x\left(x+1\right)}=\frac{9}{10}\)

\(\Rightarrow\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{9}{10}\)

\(\Rightarrow\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{9}{10}\)

\(\Rightarrow\frac{1}{1}-\frac{1}{x+1}=\frac{9}{10}\)

\(\Leftrightarrow\frac{x+1-1}{x+1}=\frac{9}{10}\)

\(\Rightarrow\frac{x}{x+1}=\frac{9}{10}\)

\(\Rightarrow x=9\)

b) \(\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{13.15}+x=\frac{1}{3}\)

\(\Leftrightarrow\frac{5-3}{3.5}+\frac{7-5}{5.7}+...+\frac{15-13}{13.15}+x=\frac{1}{3}\)

\(\Leftrightarrow\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{13}-\frac{1}{15}+x=\frac{1}{3}\)

\(\Leftrightarrow\frac{1}{3}-\frac{1}{15}+x=\frac{1}{3}\)

\(\Leftrightarrow x=\frac{1}{15}\)

a: \(\left[\left(10-x\right)\cdot2+51\right]:3-2=3\)

=>\(\left[2\left(10-x\right)+51\right]:3=5\)

=>\(\left[2\left(10-x\right)+51\right]=15\)

=>\(2\left(10-x\right)=15-51=-36\)

=>10-x=-36/2=-18

=>\(x=10-\left(-18\right)=10+18=28\)

b: \(\left(x-12\right)-15=20-\left(17+x\right)\)

=>\(x-12-15=20-17-x\)

=>\(x-27=3-x\)

=>\(2x=30\)

=>\(x=\dfrac{30}{2}=15\)

c: \(720-\left[41-\left(2x-5\right)\right]=2^3\cdot5\)

=>\(720-\left[41-2x+5\right]=8\cdot5=40\)

=>\(\left[41-2x+5\right]=720-40=680\)

=>-2x+46=680

=>-2x=680-46=634

=>\(x=\dfrac{634}{-2}=-317\)