Question
Solve using formula.
$5 x^2+13 x+8=0$
$5 x^2+13 x+8=0$
✓
Answer
$5 x^2+13 x +8=0 \text { compare with } ax ^2+ bx + c =0$
$ \Rightarrow a =5, b=13 \text { and } c =8 $
$ \therefore b ^2-4 ac =13^2-4(5)(8) $
$ =169-160$
$=9$
$ x =\frac{- b \pm \sqrt{ b ^2-4 a c}}{2 a }$
$\Rightarrow x =\frac{-13 \pm \sqrt{9}}{2 \times 5} $
$ \Rightarrow x =\frac{-13 \pm 3}{10}$
$ \Rightarrow x =\frac{-13+3}{10} \text { or } x =\frac{-13-3}{10} $
$ \Rightarrow x =\frac{-10}{10} \text { or } x =\frac{-16}{10} $
$ \Rightarrow x =-1 \text { or } x =-\frac{8}{5}$
$ \Rightarrow a =5, b=13 \text { and } c =8 $
$ \therefore b ^2-4 ac =13^2-4(5)(8) $
$ =169-160$
$=9$
$ x =\frac{- b \pm \sqrt{ b ^2-4 a c}}{2 a }$
$\Rightarrow x =\frac{-13 \pm \sqrt{9}}{2 \times 5} $
$ \Rightarrow x =\frac{-13 \pm 3}{10}$
$ \Rightarrow x =\frac{-13+3}{10} \text { or } x =\frac{-13-3}{10} $
$ \Rightarrow x =\frac{-10}{10} \text { or } x =\frac{-16}{10} $
$ \Rightarrow x =-1 \text { or } x =-\frac{8}{5}$
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