a)<=> 4x^2 - 4x - (x^2 - 9) = 9
<=> 4x^2 - 4x - x^2 = 0
<=> 3x^2 - 4x = 0 <=> x(3x - 4) = 0
<=> x = 0 hoặc x = 4/3
b)<=> \(\dfrac{x^2+1}{\left(x-2\right)x}=1\Leftrightarrow x^2+1=x^2-2x\Leftrightarrow2x-1=0\Leftrightarrow x=\dfrac{1}{2}\)
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