-2 nhé bạn

                  (3.5+5.7)x+(3.5+5.7)+(3.5+5.7)=0

                       9.2x + 9.2 +9.2 = 0

                       9.2x +9.1 x 1 + 9.2 x 1 = 0

                      9.2( x + 1 + 1 ) = 0

                      9.2(x+2)=0

                           x + 2 = 0 : 9.2 

                           x + 2 = 0 

                           x = 0 - 2 

                           x = -2

\(\left(3.5+5.7\right)x+\left(3.5+5.7\right)+\left(3.5+5.7\right)=0\)

\(\left(3.5+5.7\right)^3.x=0\)

\(125000.x=0\)

\(\Leftrightarrow x=0\)

Đổi k ko minasan

a) Ta có 

1/1 - 1/3 + 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/x - 1/x + 2 = 5

rút gọn ta được : 1 - 1/x+2 = 5

<=> x + 2 - 1 / x+ 2

<=> x + 1 / x + 2 = 5

<=> x+ 1 = 5x + 10

<=> - 4x = 9

<=> x = -9/4

B) / x +4/ = 2^0 + 1 ^ 2013

=> /x + 4/ = 1 + 1

=> / x + 4 / = 2

TH 1 :  x+ 4 = 2

 => x = 2 - 4 = -2

TH2 : x + 4 = -2

=> x = -2 - 4 = -6

=> x = { - 2 , -6 }

Ta có: (5x+3⁴).6⁸=6⁹.3⁴

    => 5x + 3⁴       = 6⁹.3⁴:6⁸

   => 5x + 3⁴        = 3⁴.6 = 486

   => 5x                = 486 : 3⁴ = 6

   => x                  = 6:5 = 1,2

(5x+3^4).6^8 = 6^9.3^4

(5x+3^4)        =6^9.3^4:6^8

5x+81            =486

5x                   =486-81

5x                    =405

x                      = 405:5

x                      =81

(5x+3⁴)*6⁸=6⁹*3⁴

5x+3⁴=6⁹*3⁴/6⁸

5x+3⁴=6^9-8*3⁴

5x+3⁴=6*3⁴

5x=6*3⁴-3⁴

5x=3⁴*(6-1)

5x=3⁴*5

x=3⁴

x=81

Đề thiếu rồi. Bạn xem lại.

\(\frac{x}{1.3}+\frac{x}{3.5}+\frac{x}{5.7}+....+\frac{x}{97.99}=\frac{49}{99}\)

\(\Leftrightarrow\frac{x}{2}.\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+....+\frac{1}{97}-\frac{1}{99}\right)=\frac{49}{99}\)

\(\Leftrightarrow\frac{x}{2}.\left(\frac{1}{1}-\frac{1}{99}\right)=\frac{49}{99}\)

\(\Leftrightarrow\frac{x}{2}.\frac{98}{99}=\frac{49}{99}\)

\(\Leftrightarrow\frac{x}{2}=\frac{49}{99}\div\frac{98}{99}\)

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

\(\Leftrightarrow x=\frac{1}{2}\times2=1\)

\(\frac{x}{1\cdot3}+\frac{x}{3\cdot5}+...+\frac{x}{97\cdot99}=\frac{49}{99}\)

\(\Rightarrow\frac{x}{2}\left[\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+...+\frac{1}{97\cdot99}\right]=\frac{49}{99}\)

\(\Rightarrow\frac{x}{2}\left[\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\right]=\frac{97}{99}\)

\(\Rightarrow\frac{x}{2}\left[1-\frac{1}{99}\right]=\frac{49}{99}\)

\(\Rightarrow\frac{x}{2}\cdot\frac{98}{99}=\frac{49}{99}\)

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

=> x = 1/2 * 2 = 1