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(-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(-6)/(2(-1)) }`

Simplify:

`\mathfrak{\displaystyle(-6)/(-2)}`

`\mathfrak{3}\\=======================================`

Notes:

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