1,Tìm x: a)x/2,3=5/4 b)8:x=5:(-6) c)x-1/3=7/8 d)1,2/3,5=-6/x e)x/4=25/x g)9:(2x)=6:5

Đáp án+Giải thích các bước giải:

a)$\frac{x}{2,3}$=$\frac{5}{4}$ 

⇒4x=2,3.5

⇒4x=11,5

⇒x=2,875

b)8:x=5:(-6)

⇒8:x=$\frac{-5}{6}$ 

⇒x=8:$\frac{-5}{6}$ 

⇒x=8.$\frac{-6}{5}$ 

⇒x=9,6

c)x-1/3=7/8

⇒x=7/8+1/3

⇒x=21/24+8/24

⇒x=29/24

d)$\frac{1,2}{3,5}$=$\frac{-6}{x}$

⇒1,2x=3,5.(-6)

⇒1,2x=-21

⇒x=-21:1,2

⇒x=17,5

e)x/4=25/x

⇒x.x=4.25

⇒x²=100

⇒x=10 hoặc x=-10

g)9:(2x)=6:5

⇒9:(2x)=$\frac{6}{5}$ 

⇒2x=9:$\frac{6}{5}$ 

⇒2x=9.$\frac{5}{6}$ 

⇒2x=7,5

⇒x=7,5:2

⇒x=3,75

Answer

`a, x/{2 , 3} = 5/4`

`=> 4x = 2,3 . 5`

`=> 4x = 11,5`

`=> x = 11,5 : 4`

`=> x = 2,875`

Vậy `x = 2,875`

__________________________

`b, 8 : x = 5 : (-6)`

`=> 8/x = {-5}/6`

`=> -5x = 8 . 6`

`=> -5x = 48`

`=> x = 48 : (-5)`

`=> x = -9,6`

Vậy `x = -9,6`

__________________________

`c, x - 1/3 = 7/8`

`=> x = 7/8 + 1/3`

`=> x = 29/24`

Vậy `x = 29/24`

__________________________

`d, {1,2}/{3 , 5} = {-6}/x`

`=> 1,2x = -6 . 3,5`

`=> 1,2x = -21`

`=> x = -21 : 1,2`

`=> x = -17,5`

Vậy `x = -17,5`

__________________________

`e, x/4 = 25/x`

`=> x . x = 4 . 25`

`=> x^2 = 100`

`=> x^2 = (+-10)^2`

`=> x = +-10`

Vậy `x \in {10 ; -10}`

__________________________

`g, 9 : 2x = 6 : 5`

`=> 9/{2x} = 6/5`

`=> 2x . 6 = 9 . 5`

`=> 2x . 6 = 45`

`=> 2x = 45 : 6`

`=> 2x = 7,5`

`=> x = 7,5 : 2`

`=> x = 3,75`

Vậy `x = 3,75`