Question

Tìm \(x\), biết:
a) \(\dfrac{8}{25}=\dfrac{2^x}{5^x-1}\);
b) \(x^2-\dfrac{3}{4}x=0\).

Answer 1

`#3107.101107`

`a)`

`8/25 = (2^x)/(5^(x - 1))`

`(2^3)/(5^2) = (2^x)/(5^(x - 1))`

\(\left\{{}\begin{matrix}x=3\\x-1=2\end{matrix}\right.\\ \left\{{}\begin{matrix}x=3\\x=2+1=3\end{matrix}\right.\)

Vậy, `x = 3`

`b)`

`x^2 - 3/4x = 0`

`x(x - 3/4) = 0`

TH1: `x = 0`

TH2: `x - 3/4 = 0`

`x = 3/4`

Vậy, `x \in {0; 3/4}.`