Question

y=-x^2-6x
how do I find the vertex?

Answer 1

the vertex lies on the line of symmetry.

the line of symmetry is found using

\[x = \frac{-b}{2a}\]

in your question a = -1 and b = -6

so the line of symmetry is

\[x = \frac{- -6}{2 \times (-1)} = -3\]

this is the x value in the vertex

substitute x = -3 into the equation to find the y=value of the vertex

Answer 2

i came up with 9

Answer 3

it easier to complete the square (i don't know if you this expresion, it is a literal translation from spanish), but anyway
\[ y=-x^2-6x \]
\[ y-9=-(x^2+6x+9) \]
\[ y-9=-(x+3)^2 \]
now from this, what is the vertex?

Answer 4

the vertex is (-3, 9)