\(4\left(2x+7\right)^2-9\left(x-3\right)^2=0\)
\(\Leftrightarrow2^2\left(2x+7\right)^2-3^2\left(x-3\right)^2=0\)
\(\Leftrightarrow\left[2\left(2x+7\right)\right]^2-\left[3\left(x-3\right)\right]^2=0\)
\(\Leftrightarrow\left[4x+14\right]^2-\left[3x-9\right]^2=0\)
\(\Leftrightarrow\left(4x+14+3x-9\right)\left[\left(4x+14\right)-\left(3x-9\right)\right]=0\)
\(\Leftrightarrow\left(7x+5\right)\left(x+23\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}7x+5=0\\x+23=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=-\frac{5}{7}\\x=-23\end{array}\right.\)
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