Biết rồi mà đi đố người khác . Chịu chị luôn em lạy 2 tay

tìm n   N để \(\frac{n}{n+1}\) + \(\frac{n}{n+2}\) là số tự nhiên

giúp mik với sắp thi r

\(a,70-5\times\left(x-3\right)=45\)

\(5\times\left(x-3\right)=70-45\)

\(5\times\left(x-3\right)=25\)

\(x-3=25:5\)

x - 3 = 5

x = 5 + 3 = 8

vậy x = 8

\(b,12+\left(5+x\right)=20\)

12 + 5 + x = 20

17 + x = 20

x = 20 - 17 = 3

vậy x = 3

c, 130 - (100 + x) = 25

130 - 100 - x = 25

30 - x = 25

x = 30 - 25 = 5

vậy x = 5

\(g,10+2\times x=4^5:4^3\)

\(10+2\times x=4^2\)

\(10+2\times x=16\)

\(2\times x=16-10\)

\(2\times x=6\)

x = 6 : 2 = 3

vậy x = 3

h, \(14\times x+54=82\)

\(14\times x=82-54\)

\(14\times x=28\)

\(x=28:14=2\)

vậy x = 2

\(k,15\times x-133=17\)

\(15\times x=17+133\)

\(15\times x=150\)

\(x=150:15=10\)

vậy x = 10

\(a,70-5\times\left(x-3\right)=45\)

\(5\times\left(x-3\right)=70-45\)

\(5\times\left(x-3\right)=25\)

\(x-3=25:5\)

x - 3 = 5

x = 5 + 3 = 8

vậy x = 8

\(b,12+\left(5+x\right)=20\)

12 + 5 + x = 20

17 + x = 20

x = 20 - 17 = 3

vậy x = 3

c, 130 - (100 + x) = 25

130 - 100 - x = 25

30 - x = 25

x = 30 - 25 = 5

vậy x = 5

\(g,10+2\times x=4^5:4^3\)

\(10+2\times x=4^2\)

\(10+2\times x=16\)

\(2\times x=16-10\)

\(2\times x=6\)

x = 6 : 2 = 3

vậy x = 3

h, \(14\times x+54=82\)

\(14\times x=82-54\)

\(14\times x=28\)

\(x=28:14=2\)

vậy x = 2

\(k,15\times x-133=17\)

\(15\times x=17+133\)

\(15\times x=150\)

\(x=150:15=10\)

vậy x = 10

Trả lời

a)2x-15=17

   2x     =17-15

  2x      =2

   x       =2:2

   x       =1

b)3 1/8-1/2x=0,5

    25/8-1/2x=1/2

            1/2x=25/8-1/2

            1/2x=21/8

                 x=21/8.2/1

                 x=21/4

c)8 1/4x+2 1/3=20

   33/4x+7/3     =20

   33/4x            =20-7/3

   33/4x            =53/3

          x            =53/3.4/33

         x             =...

a) 2x - 15 = 17

2x = 17 + 15

2x = 32

x = 32 : 2 

x = 16

Vậy x = 16

b) \(3\frac{1}{3}-\frac{1}{2}x=0,5\)

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

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

\(\frac{1}{2}x=\frac{17}{6}\)

\(x=\frac{17}{6}:\frac{1}{2}\)

\(x=\frac{17}{3}\)

Vậy x = 17/3

c) \(8\frac{1}{4}x+2\frac{1}{3}=20\)

\(\frac{33}{4}x+\frac{7}{3}=20\)

\(\frac{33}{4}x=20-\frac{7}{3}\)

\(\frac{33}{4}x=\frac{53}{3}\)

\(x=\frac{53}{3}:\frac{33}{4}\)

\(x=\frac{212}{99}\)

Vậy x = 212/99

=))

`@` `\text {Ans}`

`\downarrow`

`a)`

`x + 10 = 20`

`=> x = 20 -10`

`=> x = 10`

Vậy, `x = 10`

`b)`

`2 * x + 15 = 35`

`=> 2x = 35 - 15`

`=> 2x = 20`

`=> x = 20 \div 2`

`=> x = 10`

Vậy, `x = 10`

`c)`

`3 * ( x + 2 ) = 15`

`=> x + 2 = 15 \div 3`

`=> x + 2 = 5`

`=> x = 5 - 2`

`=> x = 3`

Vậy, `x = 3`

`d)`

`10 * x + 15 * 11 = 20 * 10`

`=> 10x + 165 = 200`

`=> 10x = 200 - 165`

`=> 10x = 35`

`=> x = 35 \div 10`

`=> x = 3,5`

Vậy,` x = 3,5`

`e)`

`4 * ( x + 2 ) = 3 * 4`

`=> x + 2 = 12 \div 4`

`=> x + 2 = 3`

`=> x = 3 - 2`

`=> x = 1`

Vậy,` x = 1`

`f)`

`33 x + 135 = 26 * 9`

`=> 33x + 135 = 234`

`=> 33x = 234 - 135`

`=> 33x = 99`

`=> x = 99 \div 33`

`=> x = 3`

Vậy, `x = 3`

`g)`

`2 * x + 15 + 16 + 17 = 100`

`=> 2x + 48 = 100`

`=> 2x = 100 - 48`

`=> 2x = 52`

`=> x = 52 \div 2`

`=> x =26`

`h)`

`2 * (x + 9 + 10 + 11) = 4 . 12 . 25`

`=> 2 * (x + 9 + 10 + 11) = 4*25*12`

`=> 2 * (x + 9 + 10 + 11) = 100*12`

`=> x + 9 + 10 + 11 = 100*12 \div 2`

`=> x + 30 = 600`

`=> x = 600 - 30`

`=> x = 570`

Vậy, `x = 570.`

a) \(x+10=20\Leftrightarrow x=10\)

b) \(2x+15=35\Leftrightarrow2x=20\Leftrightarrow x=10\)

c) \(3.\left(x+2\right)=15\Leftrightarrow x+2=5\Leftrightarrow x=3\)

d) \(10x+15.11=20.10\Leftrightarrow10x+165=200\Leftrightarrow10x=35\Leftrightarrow x=\dfrac{35}{10}=\dfrac{7}{2}\)

e) \(4.\left(x+2\right)=3.4\Leftrightarrow x+2=3\Leftrightarrow x=1\)

f) \(35x+135=26.9\Leftrightarrow35x=234-135\Leftrightarrow35x=99\Leftrightarrow x=\dfrac{99}{35}\)

g) \(2x+15+16+17=100\Leftrightarrow2x+48=100\Leftrightarrow2x=52\Leftrightarrow x=26\)

h) \(2.\left(x+9+10+11\right)=4.12.25\)

\(\Leftrightarrow x+30=2.12.25\)

\(\Leftrightarrow x=600-30\)

\(\Leftrightarrow x=570\)

a, Câu hỏi của Nguyễn Ánh Ngân - Toán lớp 6 - Học toán với OnlineMath

b, Câu hỏi của Vũ Xuân Hiếu - Toán lớp 6 | Học trực tuyến

c)$x-\frac{1}{2}-\frac{1}{6}-\frac{1}{12}-\frac{1}{20}-\frac{1}{30}-\frac{1}{42}-\frac{1}{56}=\frac{5}{24}$

14) (x - 2) . (x + 4) = 0

\(\Rightarrow\) x - 2 = 0 hoặc x + 4 = 0

Nếu x - 2 = 0

x = 0 + 2

x = 2

Nếu x + 4 = 0

x = 0 - 4

x = -4

Vậy x \(\in\) {2 ; -4)

15) (x - 2) . (x + 15) = 0

\(\Rightarrow\) x - 2 = 0 hoặc x + 15 = 0

Nếu x - 2 = 0

x = 0 + 2

x = 2

Nếu x + 15 = 0

x = 0 - 15

x = -15

Vậy x \(\in\) {-15 ; 2}

a) x+15 = 20-4x

=> x=1

b) 17-x=7-6x

=> x=-2

c) -12+x=5x-20

=> x=2

d) 4x-5=15-x

=> x=4

e) 9x-7=20-6x

=>x= \(\frac{9}{5}\)

g)2.(x-10)=3.(x-20)=x-4

=> x thuộc ∅

h) (x^2+2).(x-3) <0

=> x=3,...

b, \(\dfrac{x-3}{4}=\dfrac{15}{20}\)

<=> \(\dfrac{x-3}{4}=\dfrac{3}{4}\)

=> x-3=3

<=> x=6

Vậy x=6

\(a,\dfrac{x}{15}=\dfrac{4}{y}=\dfrac{-2}{5}\)

* \(\dfrac{x}{15}=\dfrac{-2}{5}\)

\(\Rightarrow\dfrac{x}{15}=\dfrac{-6}{15}\)

\(\Rightarrow x=-6\)

*\(\dfrac{4}{y}=\dfrac{-2}{5}\)

\(\Rightarrow\dfrac{4}{y}=\dfrac{4}{-10}\)

\(\Rightarrow y=-10\)

Vậy x = - 6 ; y = - 10

\(b,\dfrac{x-3}{4}=\dfrac{15}{20}\)

=> ( x - 3 ) . 20 = 4. 15

=> 20x - 60 = 60

=> 20x = 60 + 60

=> 20x = 120

=> x = 120 : 20

=> x = 6

Vậy x = 6

\(c,\dfrac{-5}{9}+\dfrac{-8}{15}+\dfrac{22}{-9}+\dfrac{-7}{15}< x\le\dfrac{-1}{3}+\dfrac{-1}{4}+\dfrac{-5}{12}\)

\(\Rightarrow\dfrac{-5}{9}+\dfrac{-8}{15}+\dfrac{-22}{9}+\dfrac{-7}{15}< x\le\dfrac{-4}{12}+\dfrac{-3}{12}+\dfrac{-5}{12}\)

\(\Rightarrow\left(\dfrac{-5}{9}+\dfrac{-22}{9}\right)+\left(\dfrac{-8}{15}+\dfrac{-7}{15}\right)< x\le-1\)

\(\Rightarrow-3+\left(-1\right)< x\le-1\)

\(\Rightarrow-4< x\le-1\)

\(\Rightarrow x=-3;-2;-1\)