Question
Solve using formula.
x2 + 6x + 5 = 0
x2 + 6x + 5 = 0
✓
Answer
$\begin{array}{l}x^2+6 x+5=0 \\ \Rightarrow x^2+6 x+5=0 \text { compare with } a x^2+b x+c=0 \\ \Rightarrow a=1, b=6 \text { and } c=5 \\ \therefore b^2-4 a c=6^2-4(1)(5) \\ =36-20 \\ =16 \\ x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a}\end{array}$
$\begin{array}{l}x=\frac{-6 \pm \sqrt{16}}{2 \times 1}=\frac{-6 \pm 4}{2} \\ \Rightarrow x=\frac{-6+4}{2} \text { or } x=\frac{-6-4}{2} \\ \Rightarrow x=-\frac{2}{2} \text { or } x=-\frac{10}{2} \\ \Rightarrow x=-1 \text { or } x=-5\end{array}$
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