Question

giải bất phương trình 

a) \(log_5x>6\)

b) \(log_7x< 2\)

c) \(log_2x\le3\)

d) \(log_{\dfrac{1}{3}}x>27\)

Answer 1

a.

ĐKXĐ: \(x>0\)

\(log_5x>6\Rightarrow x>6^5\Rightarrow x>7776\)

b.

ĐKXĐ: \(x>0\)

\(log_7x< 2\Rightarrow\left\{{}\begin{matrix}x>0\\x< 7^2\end{matrix}\right.\) \(\Rightarrow0< x< 49\)

c. 

\(log_2x\le3\Rightarrow\left\{{}\begin{matrix}x>0\\x\le3^2\end{matrix}\right.\) \(\Rightarrow0< x\le9\)

d.

\(log_{\dfrac{1}{3}}x>27\Rightarrow\left\{{}\begin{matrix}x>0\\x< \left(\dfrac{1}{3}\right)^{27}\end{matrix}\right.\)

\(\Rightarrow0< x< \dfrac{1}{3^{27}}\)