Câu 6: Khôg có cau nào đúng

Câu 7: C

Câu 8: B

Câu 9: B

Câu 10: D

6Không có đáp án nào đúng x=11/4

7C

8B

9B

10D

`3/4 + x/20 = 4/5`

`=> x/20 = 4/5 - 3/4`

`=> x/20 = 16/20 - 15/20`

`=> x/20=1/20`

`=>x=1`

a: \(\Leftrightarrow\left|\dfrac{5}{3}x\right|=\dfrac{1}{6}\)

\(\Leftrightarrow\left[{}\begin{matrix}x\cdot\dfrac{5}{3}=\dfrac{1}{6}\\x\cdot\dfrac{5}{3}=-\dfrac{1}{6}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{6}:\dfrac{5}{3}=\dfrac{3}{30}=\dfrac{1}{10}\\x=-\dfrac{1}{10}\end{matrix}\right.\)

b: \(\Leftrightarrow\left|\dfrac{3}{4}x-\dfrac{3}{4}\right|=\dfrac{3}{4}+\dfrac{3}{4}=\dfrac{3}{2}\)

\(\Leftrightarrow\left|x-1\right|=\dfrac{3}{2}:\dfrac{3}{4}=2\)

=>x-1=2 hoặc x-1=-2

=>x=3 hoặc x=-1

c: \(\Leftrightarrow\left|x+\dfrac{3}{5}\right|=\left|x-\dfrac{7}{3}\right|\)

\(\Leftrightarrow x+\dfrac{3}{5}=\dfrac{7}{3}-x\)

=>2x=44/15

hay x=22/15

\(\frac{x-2}{x-1}=\frac{x+4}{x-7}\)

<=>(x-2)(x-7)=(x-1)(x+4)

<=>x²-9x+14=x²+3x-4

<=>x²-9x-x²-3x=-4-14

<=>-12x=-18

<=>x=\(\frac{3}{2}\)

2,\(\frac{x+4}{20}=\frac{5}{x+4}\)

<=>(x+4)²=100

<=>x²+8x+16=100

<=>x²+8x-84=0

<=>x²+14x-6x-84=0

<=>x(x+14)-6(x+14)=0

<=>(x-6)(x+14)=0

<=>\(\orbr{\begin{cases}x-6=0\\x+14=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=6\\x=-14\end{cases}}}\)

  \(x+x+\frac{3}{4}\times\frac{4}{5}+x+\frac{8}{20}=136\)

 \(3x+\frac{3}{4}\times\frac{4}{5}+\frac{8}{20}=136\)

\(3x+1=136\)

\(3x=136-1\)

\(3x=135\)

\(x=135:3\)

\(x=45\)

( x - 4 ) x 5 = - 20 x ( 4 - x )

5 x - 20     = - 80 + 20 x

5 x - 20 x  = - 80 + 20

- 15 x        = - 60

      x         = 4

số x đó là

4

nhe 

mình mới biết nên

vào ko ko biết gì

(x-4)x5= -20x(4-x)

=>5x-20= -80+20x

=>5x-20x=-80+20

=>5x-20x=-60

=>-15x=-60

=>x=-60 :(-15)

=> x= 4

\(\frac{x+4}{20}=\frac{5}{x+4}\Rightarrow\left(x+4\right).\left(x+4\right)=5.20\)

\(\left(x+4\right)^2=100\)

\(\left(x+4\right)^2=10^2\text{ hoặc }\left(x+4\right)^2=\left(-10\right)^2\)

\(\Rightarrow x+4=10\text{ hoặc }x+4=-10\)

\(x=6\text{ hoặc }x=-14\)

a: x-4/5=3/7

=>x=3/7+4/5=43/35

b: x+3/7=4/5

=>x=4/5-3/7=13/35

c: 19/20-x=8/5-3/4

=>19/20-x=32/20-15/20=17/20

=>x=2/20=1/10

d: =>4/5*x=2/21

=>x=2/21:4/5=5/42

e: =>x:7/9=6/8

=>x=6/8*7/9=3/4*7/9=21/36=7/12

f: =>x/6=2/3-1/3=1/3

=>x=2