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a)
$2x^2+9x-5$
$x=\frac{-9\pm\sqrt{9^2-4\cdot2\cdot\left(-5\right)}}{4}=\frac{-9\pm\sqrt{121}}{4}$
$\frac{-9+11}{4}=\frac{1}{2}\ tai\ \frac{-20}{4}=-5$
$2\left(x-\frac{1}{2}\right)\left(x+5\right)$
b)
$3x^2-7x-6$
$x=\frac{7\pm\sqrt{121}}{6}=\frac{7+11}{6}=3\ tai\ \frac{7-11}{6}=-\frac{2}{3}$
$3\left(x-3\right)\left(x+\frac{2}{3}\right)$