\(\Leftrightarrow\frac{30}{x-3}-\frac{30}{x}=\frac{90}{\left(x-3\right)x}\)
\(\Rightarrow\frac{90}{\left(x-3\right)x}=\frac{1}{2}\)
\(\Rightarrow-\frac{30}{x}+\frac{30}{x-3}-\frac{1}{2}=0\)
\(\Rightarrow-\frac{x^2-3x-180}{2\left(x-3\right)x}=0\)
=>x2-3x-180=0
denta:(-3)2-(-4(1.180))=729>0
=>pt co 2 nghiem
\(x_{1,2}=\frac{-b\pm\sqrt{\Delta}}{2a}=\frac{3\pm\sqrt{729}}{2}\)
x1=(3+27):2=15
x2=(3-27):2=-12
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