a: 86-x>86-4

=>-x>-4

hay x<4

b: x+28<28+3

=>x+28<31

hay x<3

x=0,1,2,3

x=0,1,2

a,86-x>86-4

86-x > 82

-x > 82 -86

-x> -4

x< 4

b,x+28<28+3

x+ 28 < 31

=> x < 31 - 28 

x < 3

6.4^\(x\).4¹ + 4\(^x\).4\(^3\) = 2⁸.(7 + 15)

4\(^x\).(6.4 + 4³) = 2⁸.22

4\(^x\).(24 + 64) = 256.22

4\(^x\). 88 =       5632

4\(^x\)      = 532 : 88

4\(^x\)     = 64

4\(^x\)     = 4³

\(x\) = 3 

\(\dfrac{4x-5}{7-4x}=\dfrac{7x-28}{26-7x}\)

\(\Leftrightarrow104x-28x^2-130+35x=49x-28x^2-196+112x\)

\(\Leftrightarrow-22x=-66\)

hay x=3

\(\Rightarrow\left(4x-5\right)\left(26-7x\right)=\left(7-4x\right)\left(7x-28\right)\\ \Rightarrow104x-28x^2-130+35x=49x-196-28x^2+112x\\ \Rightarrow-22x=-66\Rightarrow x=3\)

b) (4x -1)² = (1-4x)⁴  (1)

Vì (1 - 4x) = (4x - 1)

\(\Rightarrow\)(1 - 4x)⁴ = [ -( 4x -1)⁴ ]

Vì (1-4x)⁴ = ( 4x - 1)⁴

Do đó (1) có dạng :

(4x - 1)²  = (4x - 1)²

Đặt 4x - 1 = x, ta có : 

x²  = x⁴

x²  ( 1 - x² ) = 0

\(\Rightarrow\)\(\orbr{\begin{cases}x=0\\x^2=\orbr{\begin{cases}1^2\\\left(-1\right)^2\end{cases}}\end{cases}}\)\(\Leftrightarrow\)\(\orbr{\begin{cases}x=0\\x=\orbr{\begin{cases}x=1\\x=-1\end{cases}}\end{cases}}\)

Thay x = 4x -1 = 0 

         x = \(\frac{1}{4}\)

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

                                   x = 0

Vậy  x = \(\frac{1}{2}\) hoặc x = 0

x = \(\frac{1}{4}\) nữa bạn nhé

4x / 101 = 28

4x = 28 x101 

4x =2828

x = 2828 / 4

x =707

nhớ k cho mình nha

4x = 28x101

4x = 21008

 x = 21008 : 4

 x = 5252 

4x : 101 = 28

4x = 28 . 101

4x = 2828

x  = 2828 : 4

x = 704

\(4x+28=134\)

\(4x=134-28\)

\(4x=106\)

\(x=106:4\)

\(x=26,5\)

-4x-28=22

-4x =22+28

-4x =50

x =50:-4

x = 15,5

vậy x =15,5