ĐKXĐ: \(x\notin\left\{10;-10\right\}\)
Ta có: \(\dfrac{720}{x+10}+4=\dfrac{720}{x-10}\)
\(\Leftrightarrow\dfrac{720\left(x-10\right)}{\left(x+10\right)\left(x-10\right)}+\dfrac{4\left(x^2-100\right)}{\left(x+10\right)\left(x-10\right)}=\dfrac{720\left(x+10\right)}{\left(x+10\right)\left(x-10\right)}\)
Suy ra: \(720x-7200+4x^2-400-720x-7200=0\)
\(\Leftrightarrow4x^2=14800\)
\(\Leftrightarrow x^2=3700\)
hay \(x\in\left\{10\sqrt{37};-10\sqrt{37}\right\}\)
ĐKXĐ: \(x\ne\pm10\)
\(\Leftrightarrow\dfrac{180}{x-10}-\dfrac{180}{x+10}=1\)
\(\Leftrightarrow\dfrac{180\left(x+10-x+10\right)}{\left(x-10\right)\left(x+10\right)}=1\)
\(\Leftrightarrow\dfrac{3600}{x^2-100}=1\)
\(\Rightarrow x^2-100=3600\)
\(\Leftrightarrow x^2=3700\)
\(\Leftrightarrow x=\pm10\sqrt{37}\) (thỏa mãn)
