Question

Find the vertex of this parabola: y = -x2 + 6x – 15

Answer 1

$y = - x {}^{2} + 6x - 15$

$y {}^{ \gamma } = - 2x + 6$

$y {}^{ \gamma } = 0$

$- 2x + 6 = 0$

$- 2x = - 6$

$2x = 6$

$x = 3$

Substitute x=3 in y=-x²+6x-15

$y = - (3) {}^{2} + 6(3) - 15$

$y = - 9 + 18 - 15$

$y = - 9 + 3$

$y = - 6$

Vertex: (3,-6)

Answer 2

hello!

$==============================$

In order to find the vertex of a parabola, we use the following formula:

$\mathfrak{\displaystyle\frac{-b}{2a} }$

Please remember that a parabola looks like this:

$\tt{y=ax^2+bx+c}$

Now you know what a and b stand for.

In this case, a = -1, and b is 6:

$\mathfrak{\displaystyle\frac{-6}{2(-1)} }$

Simplify:

$\mathfrak{\displaystyle\frac{-6}{-2}}$

$\mathfrak{3}\\=======================================$

Notes:

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