\(\Leftrightarrow\left(64x^2+80x+25\right)\left(8x^2+10x+3\right)=9\)
Đặt \(8x^2+10x+3=t\Rightarrow64x^2+80x+25=8t+1\)
\(\left(8t+1\right)t-9=0\)
\(\Leftrightarrow8t^2+t-9=0\Rightarrow\left[{}\begin{matrix}t=1\\t=-\frac{9}{8}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}8x^2+10x+3=1\\8x^2+10x+3=-\frac{9}{8}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}8x^2+10x+2=0\\8x^2+10x+\frac{33}{8}=0\left(vn\right)\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=-1\\x=-\frac{1}{4}\end{matrix}\right.\)
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