(5+6,5)x = 875-1-1

11,5x = 873

x = 873:11,5

x = \(\frac{1746}{23}\)

a) Áp dụng tính chất dãy tỉ số bằng nhau , ta có :

\(\dfrac{3x+2}{5x+7}=\dfrac{3x-1}{5x+1}=\dfrac{3x+2-3x+1}{5x+7-5x-1}=\dfrac{3}{6}=\dfrac{1}{2}\)

\(\Rightarrow\left\{{}\begin{matrix}3x+2=\dfrac{5x+7}{2}\\3x-1=\dfrac{5x+1}{2}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}6x+4=5x+7\\6x-2=5x+1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=3\\x=3\end{matrix}\right.\)(Nhận)

Vậy x = 3

b) Giống vậy :)

a, \(\dfrac{3x+2}{5x+7}=\dfrac{3x-1}{5x+1}\)

\(\Leftrightarrow\left(3x+2\right)\left(5x+1\right)=\left(5x+7\right)\left(3x-1\right)\)

\(\Leftrightarrow15x^2+3x+10x+2=15x^2-5x+21x-7\)

\(\Leftrightarrow15x^2+13x=15x^2+16x-9\)

\(\Leftrightarrow3x=9\)

\(\Leftrightarrow x=3\)

Vậy x = 3

b, Tương tự

Sử dụng tích chéo nha bạn!

a) 2^{x - 1} + 2^{x + 1} = 20

=> 2^x : 2 + 2^x . 2 = 20

=> 2^x . 1/2 + 2^x . 2 = 20

=> 2^x.(1/2 + 2)        = 20

=> 2^x . 5/2               = 20

=> 2^x                        = 20 : 5/2

=> 2^x                         = 8

=> 2^x                          = 2³

=>   x                          = 3

Xem lại đề ! 

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\(5^{x+1}+6.5^{x+1}=875\)

\(\Rightarrow5^{x+1}.\left(1+6\right)=875\)

\(\Rightarrow5^{x+1}.7=875\)

\(\Rightarrow5^{x+1}=875:7=125\)

\(\Rightarrow5^{x+1}=5^3\)

\(\Rightarrow x+1=3\)

\(\Rightarrow x=3-1=2\)