x - 4/5 = 3/7

x = 3/7 + 4/5

x = 43/35

x + 3/7 = 4/5

x = 4/5 - 3/7

x = 13/35

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

19/20 - x =  17/20

x = 19/20 - 17/20

x = 2/20 = 1/10

4/5 x X = 6/9 - 4/7

4/5 x X = 2/21

x = 2/21 : 4/5

x =5/42

x : 7/9 = 6/8

x = 6/8 x 7/9

x = 7/12

2/3 - x/6 = 6/18

x/6 = 2/3 - 6/18

x/6 = 1/3

x/6 = 2/6

=> x =2

1. x = 43/35

2. x = 13/35

3. x = 1/10

còn lại tự tính nhá

tui bận òi

3: Ta có: \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x-1\right)\left(x+1\right)=27\)

\(\Leftrightarrow x^3-27-x^3+x=27\)

hay x=54

\(A=-x^2-5\)

Vì \(-x^2\le0\Leftrightarrow-x^2-5\le-5\)

Vậy \(A_{max}=-5\Leftrightarrow x=0\)

x=0

Biểu thức này ko tồn tại cả min lẫn max

\(\dfrac{1}{M}=\dfrac{\sqrt{x}-1}{2\sqrt{x}+4}=\dfrac{-\dfrac{1}{4}\left(2\sqrt{x}+4\right)+\dfrac{\sqrt{x}}{2}}{2\sqrt{x}+4}=-\dfrac{1}{4}+\dfrac{\sqrt{x}}{4\left(\sqrt{x}+2\right)}\)

Do \(\left\{{}\begin{matrix}\sqrt{x}\ge0\\\sqrt{x}+2>0\end{matrix}\right.\) \(\Rightarrow\dfrac{\sqrt{x}}{4\left(\sqrt{x}+2\right)}\ge0\)

\(\Rightarrow\dfrac{1}{M}\ge-\dfrac{1}{4}\)

Dấu "=" xảy ra khi \(x=0\)

x - 6 : 2 ( 48 - 24 ) : 2 : 6 - 3 = 0

x - 6 : 2 . 24 : 2 : 6 - 3 = 0

x - 6 - 3 = 0

x - 9 = 0

     x = 9

x-6:2 ( 48-24) :2 :6 - 3 = 0

=>x-6:2(48-24):2:6= 3

=> x-6:2(48-24):2 = 18

=> x-6:2(48-24)= 36

=> x- 6:2. 24= 36

=> x- 6: 48= 36

=>x +8=36

=> x= 36-8

=>x= 28

x - 6 : 2 (48 - 24) : 2 : 6 - 3 = 0

x-6:2(24):2:6 =3

x-6:48 =3.6.2

x-6:48 =36

x-6 =36.48

x-6 =1728

x =1734

bằng189/15

7/2 + 7/3 x 6/5 = 7/2 + 42/15 = 189/30 = 63/10

7/2+7/3×6/5

=7/2+30/15

=7/2+1/2

=8/2=4

Chúc các bạn học tốt

`x/(2*2)+x/(3*4)+x/(6*4)+x/(8*5)+x/(10*6)=5`

`x/4 +x/12 +x/24 +x/45 + x/60 =5`

`x(1/4 +1/12 +1/24 +1/40 +1/60)=5`

`x( (30+10+5+3+2)/120 ) =5`

`x *50/120 =5`

`x = 5 *120/50 =12`

\(\dfrac{x}{4}+\dfrac{x}{12}+\dfrac{x}{24}+\dfrac{x}{40}+\dfrac{x}{60}=5\)

\(\Leftrightarrow x\left(\dfrac{1}{4}+\dfrac{1}{12}+\dfrac{1}{24}+\dfrac{1}{40}+\dfrac{1}{60}\right)=5\)

\(\Leftrightarrow x.\dfrac{5}{12}=5\)

\(\Leftrightarrow x=12\)

thanks tv cuber nhé

77/45

7/6

29/10

\(\dfrac{3}{5}+\dfrac{4}{3}\times\dfrac{5}{6}=\dfrac{3}{5}+\dfrac{10}{9}=\dfrac{27}{45}+\dfrac{50}{45}=\dfrac{77}{45}\)

\(2-\dfrac{7}{6}+\dfrac{1}{3}=\dfrac{12}{6}-\dfrac{7}{6}+\dfrac{2}{6}=\dfrac{7}{6}\)

\(\dfrac{7}{6}\times3-\dfrac{3}{5}=\dfrac{7}{2}-\dfrac{3}{5}=\dfrac{35}{10}-\dfrac{6}{10}=\dfrac{29}{10}\)

giải chi tiết đi