a) \(x:\frac{1}{2}=4\)

\(x=4\times\frac{1}{2}\)

\(x=2\)

b)\(x\times\frac{3}{5}=15\)

\(x=15:\frac{3}{5}\)

\(x=25\)

a) \(\text{X}\div\frac{1}{2}=4\)

\(\text{X}=4\times\frac{1}{2}\)

\(\text{X}=2\)

b) \(\text{X}\times\frac{3}{5}=15\)

\(\text{X}=15\div\frac{3}{5}\)

\(\text{X}=25\)

Giải đáp

a) x = 4 x 1/2

x = 2

b) x = 15 : 3/5

x = 75/3

x = 25
Học tốt

2/3

4

\(\dfrac{13}{15}-\dfrac{1}{5}=\dfrac{13}{15}=\dfrac{3}{15}=\dfrac{10}{15}=\dfrac{2}{3}\)

\(\dfrac{7}{8}\times\dfrac{2}{7}=\dfrac{14}{56}=\dfrac{1}{4}\)

1. a) -0,35 = -7/20 ; b) 1,14 = 57/50

  c) 2,108 = 527/250 ; -0,725 = -29/40

2. a) 0,2(3) = 0,2 + 0,0(3) = 0,2 + 0,3. 0,(1) = 0,2 + 0,3.1/9 = 1/5 + 1/30 = 7/30 

  b 1,4(51) = 1,4 + 0,0(51) = 7/5 + 5,1. 0,(01) = 7/5 + 5,1. 1/99 = 7/5 + 17/330 = 479/330

  c) -2,(412) = -2 - 0,(412) = -2 - 412. 0,(001) = -2 - 412. 1/999 = -2 - 412/999 = -2410/999

d) 3,1(45) = 3,1 + 0,0(45) = 3,1 + 4,5. 0,(01) = 3,1 + 4,5 . 1/99 = 3,1 + 1/22 = 173/55

3. Ta có: -2,(6).x = 0,1(6)

=> [-2 - 0,(1).6].x = (0,1 + 0,6. 0,(1)]

=> (-2 - 2/3)x = 0,1 + 1/15

=> -8/3x = 1/6

=>  x = 1/6 : (-8/3)

=> x = -1/16

Bài làm:

Theo đề ta có: | x - 1.7 | - | x - 2,4 | = 0

\(\Rightarrow\)x - 1,7 = 0 và x - 2,4 = 0

* x - 1,7 = 0

  x         = 0 + 1,7

  x         = 1,7

* x - 2,4 = 0

  x         = 0 + 2,4

  x         = 2,4

Vậy x có 2 giá trị,

nên  \(x\left\{1,7;2,4\right\}\)

lx-1.7l-lx-2.4l=0

=> lx-1.7l=lx-2.4l => x thuộc rỗng ( không có giá trị x )

(x+1/2)+(x+1/4)+(x+1/8)+(x+1/6)=1

(x+x+x+x)+(1/2+1/4+1/6+1/8)=1

4x+(12/24+6/24+4/24+3/24)=1

4x+25/24=1

4x=1-25/24

4x=-1/24

x=-1/24:4

x=-1/96

\(\dfrac{3}{7}:x=\dfrac{5}{7}\)

      \(x=\dfrac{3}{7}:\dfrac{5}{7}\)

     \(x=\dfrac{3}{7}\times\dfrac{7}{5}\)

     \(x=\dfrac{21}{35}\) 

     \(x=\dfrac{3}{5}\)

\(\dfrac{3}{7}:x=\dfrac{5}{7}\\ x=\dfrac{3}{7}:\dfrac{5}{7}\\ x=\dfrac{3}{5}\)

Vậy `x=3/5`

`@An`

\(x:\dfrac{1}{8}=\dfrac{6}{11}\\ x=\dfrac{6}{11}\times\dfrac{1}{8}\\ x=\dfrac{3}{44}\)

3/44

x = 6/11×1/8

x = 6/88

x=3/44