Question
Solve using formula.
$x^2-3 x-2=0$
$x^2-3 x-2=0$
✓
Answer
$x^2+3 x-2=0 \text { compare with } a x^2+b x+c=0 $
$\Rightarrow a=1, b=3 \text { and } c=-2$
$ \therefore b^2-4 a c=3^2-4(1)(-2) $
$ =9+8 $
$ =17 $
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} $
$\Rightarrow x=\frac{-3 \pm \sqrt{17}}{2 \times 1} $
$\Rightarrow x=\frac{-3 \pm \sqrt{17}}{2} $
$\Rightarrow x=\frac{-3+\sqrt{17}}{2} \text { or } x=\frac{-3-\sqrt{17}}{2}$
$\Rightarrow a=1, b=3 \text { and } c=-2$
$ \therefore b^2-4 a c=3^2-4(1)(-2) $
$ =9+8 $
$ =17 $
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} $
$\Rightarrow x=\frac{-3 \pm \sqrt{17}}{2 \times 1} $
$\Rightarrow x=\frac{-3 \pm \sqrt{17}}{2} $
$\Rightarrow x=\frac{-3+\sqrt{17}}{2} \text { or } x=\frac{-3-\sqrt{17}}{2}$
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