Find range of $x$ if $\log_5\left(6+\frac{2}{x}\right)+\log_{1/5}\left(1+\frac{x}{10}\right)\leq1$

inequalitylogarithms

If $\log_5\left(6+\dfrac{2}{x}\right)+\log_{1/5}\left(1+\dfrac{x}{10}\right)\leq1$, then $x$ lies in _______

My Attempt

$$
\log_5\bigg(6+\dfrac{2}{x}\bigg)+\log_{1/5}\bigg(1+\dfrac{x}{10}\bigg)=\log_5\bigg(6+\dfrac{2}{x}\bigg)-\log_{5}\bigg(1+\dfrac{x}{10}\bigg)\leq1\\
\log_5\frac{(6x+2)10}{x(10+x)}\leq1\implies\frac{(6x+2)10}{x(10+x)}\leq5\\
\frac{4(3x+1)}{x^2+10x}\leq1\\
\implies 12x+4\leq x^2+10x\quad\text{or}\quad12x+4>x^2+10x\\
x^2-2x-4\geq0\quad\text{or}\quad x^2-2x-4<0\implies x\in\mathcal{R}
$$

My reference gives the solution $(-\infty,1-\sqrt{5})\cup(1+\sqrt{5},\infty)$, what is going wrong here ?

Best Answer

You forgot to check when $$6+\dfrac{2}{x}>0$$ and $$1+\dfrac{x}{10}>0$$

is true!

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