`(2x - 5)(2x + 1) = (2x - 5)(x + 4)`

`(2x - 5)(2x + 1) - (2x - 5)(x +4) = 0`

`(2x - 5)[(2x + 1) - (x + 4)]=0`

`(2x - 5)(2x + 1 - x - 4) = 0`

`(2x - 5)(x - 3) = 0`

\(\left[{}\begin{matrix}2x-5=0\\x-3=0\end{matrix}\right.\\ \left[{}\begin{matrix}2x=5\\x=3\end{matrix}\right.\\ \left[{}\begin{matrix}x=\dfrac{5}{2}\\x=3\end{matrix}\right.\)

(2\(x-5\)).(2\(x+1\)) = (2\(x-5\)).(\(x+4\))

(2\(x-5\))(2\(x+1\)) - (\(2x-5\)).(\(x+4\)) = 0

(2\(x-5\))[2\(x+1\) - \(x-4\)] = 0

 (2\(x-5\)).[(2\(x-x\)) - (4 - 1)] = 0

  (2\(x\) - 5).[\(x\) - 3] = 0

   \(\left[{}\begin{matrix}2x-5=0\\x-3=0\end{matrix}\right.\)

    \(\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=3\end{matrix}\right.\)

Vậy \(x\) \(\in\) {\(\dfrac{5}{2}\); 3} 

tính từng bước nha

52,7 8,5 6,2 170 0

5² - 2x = -11

25 - 2x = - 11

 2x       = 25 - ( - 11 )

 2x        =   36

   x        =  36 : 2

   x        = 18

Vẫy x = 18

`5^2 - 2x = -11`

`=> 25 - 2x = -11`

`=> 2x = 25 - (-11) `

`=> 2x = 25 + 11`

`=> 2x = 36`

`=> x = 36 : 2`

`=> x = 18`

Vậy ...

\(\dfrac{16}{2^x}\) = 2

\(\dfrac{2^4}{2^x}\) = 2

2^\(4-x\) = 2¹

 4 - \(x=1\)

      \(x=4-1\)

     \(x=2\)

Vậy \(x=3\) 

Cách hai: \(\dfrac{16}{2^x}\) = 2

                2\(^x\) = 16 : 2

               2\(^x\) = 8

                2\(^x\) = 2³

                  \(x=3\)

Vậy \(x=3\) 

`270 - (3^2 xx 2 + 7^15 : 7^13)`

`= 270 - (9 xx 2 + 7^(15-13))`

`= 270 - (18 + 7^2)`

`= 270 - (18 + 49)`

`= 270 - 67`

`= 203`

270 - ( 3² . 2 + 7¹⁵ + 7¹³ )

= 270 - ( 9 . 2 + 7² )

= 270 - ( 18 + 49 )

= 270 - 67

= 203

( - 1127 - 785 ) - ( 85 - 127 + 215 )

= - 1127 - 785 - 85 + 127 - 215

= ( - 1127 + 127 ) - ( 785 + 215 ) - 85

=   - 1000 - 1000 - 85

= - 2000 - 85

= - 2085

`(-1127-785)-(85-127+215)`

`= -1127-785-85+127-215`

`= -(1127-127)-(785+215)-85`

`= -1000-1000-85`

`= -2085`

a; (\(\sqrt{45}\) - \(\sqrt{125}\) + \(\sqrt{20}\)) : \(\sqrt{5}\)

   =  (\(\sqrt{9.5}\) - \(\sqrt{25.5}\) + \(\sqrt{4.5}\)):\(\sqrt{5}\)

   =  (3\(\sqrt{5}\) - 5\(\sqrt{5}\) + 2\(\sqrt{5}\)): \(\sqrt{5}\)

     = (- 2\(\sqrt{5}\) + 2\(\sqrt{5}\)) : \(\sqrt{5}\)

     = 0 : \(\sqrt{5}\)

     = 0 

cuu t

=2,67

69 : 25 = 2,76