Parabolas
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Question

Write the equation of the parabola $y=-x^{2}-10x-5$ in the standard form. Then determine the vertex, focus, directrix and the axis of symmetry of the parabola. Also, state which way the parabola opens.

Answer

$y=-x^{2}-10x-5$

$y=-1\left(x^{2}+10x\right)-5$

$y=-1\left(x^{2}+10x+25\right)+25-5$

$y=-1\left(x+5\right)^2+20$

$y-20= -1\left(x+5\right)^2$

The parabola opens down words.

The vertex is given by $V\left(-5,20\right)$

The focus is given by $F\left(-5,\frac{79}{4}\right)$

The directrix is given by $y= \frac{81}{4}$

The axis of symmetry is given by $x=-5$