B2: Tìm x:
a) \(9\left(2x+3\right)^2=4\left(5x-2\right)^2\)
\(\Rightarrow\sqrt{9\left(2x+3\right)^2}=\sqrt{4\left(5x-2\right)^2}\)
\(\Rightarrow3\left(2x+3\right)=2\left(5x-2\right)\)
\(\Leftrightarrow6x+9-10x+4=0\)
\(\Leftrightarrow-4x+13=0\Leftrightarrow-4x=-13\)
<=> \(x=\dfrac{13}{4}\)
b) (x - 2)(x + 5) = -12
<=> x2 + 5x - 2x - 10 = -12
<=> x2 + 3x - 10 + 12 = 0
<=> x2 + 3x + 2 = 0
<=> x2 + 2.1,5.x + 2,25 = 0,25
<=> (x + 1,5)2 = 0,25
<=> \(\left[{}\begin{matrix}x+1,5=0,5\\x+1,5=-0,5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=-2\end{matrix}\right.\)