How do you find the vertex of a parabola $y=x^2+2x-1$ ?

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Answer 1 · 2015-04-10T18:16:33

The vertex of a parabola occurs when its derivative is equal to $0$

$y = x^2+2x-1$

$y' = 2x +2 = 0$ for the vertex
that is
$x=-1$ at the vertex

Substituting $x=-1$ back into the original equation gives
$y = (-1)^2+2(-1)-1$
$=1 -2 -1 = -3$

So the vertex of the parabola occurs at $(-1,-3)$

How do you find the vertex of a parabola y=x^2+2x-1y=x^2+2x-1?