Question
Solve the equation $3x^2 – x – 7 = 0$ and give your answer correct to two decimal places.
✓
Answer
$3 x^2-x-7=0 $
$ a=3, b=-1, c=-7$
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} $
$ =-\frac{(-1) \pm \sqrt{(-1)^2-4.3 \cdot(-7)}}{2 \times 3} $
$ =\frac{1 \pm \sqrt{1+84}}{6} $
$ =\frac{1 \pm \sqrt{85}}{6}$
$ =\frac{1 \pm 9 \cdot 216}{6}$
$x=\frac{1+9.216}{6} \text { and } \frac{1-9.216}{6} $
$=\frac{10.216}{6} \text { and }-\frac{8.216}{6}$
$= 1.703$ and $-1.37$
$ a=3, b=-1, c=-7$
$x=\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} $
$ =-\frac{(-1) \pm \sqrt{(-1)^2-4.3 \cdot(-7)}}{2 \times 3} $
$ =\frac{1 \pm \sqrt{1+84}}{6} $
$ =\frac{1 \pm \sqrt{85}}{6}$
$ =\frac{1 \pm 9 \cdot 216}{6}$
$x=\frac{1+9.216}{6} \text { and } \frac{1-9.216}{6} $
$=\frac{10.216}{6} \text { and }-\frac{8.216}{6}$
$= 1.703$ and $-1.37$
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