Solve using formula. x2 – 3x – 2 = 0 - Vidyadip

Question

Solve using formula.
x² – 3x – 2 = 0

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Answer

$\begin{array}{l}x^2+3 x-2=0 \text { compare with } a x^2+b x+c=0 \\ \Rightarrow a=1, b=3 \text { and } c=-2 \\ \therefore b^2-4 a c=3^2-4(1)(-2) \\ =9+8 \\ =17 \\ x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} \\ \Rightarrow x=\frac{-3 \pm \sqrt{17}}{2 \times 1}\end{array}$
$\begin{array}{l}\Rightarrow x=\frac{-3 \pm \sqrt{17}}{2} \\ \Rightarrow x=\frac{-3+\sqrt{17}}{2} \text { or } x=\frac{-3-\sqrt{17}}{2}\end{array}$

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