How do you find the vertex of # f(x)= -x^2-6x-5#?

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Answer 1 · 2015-06-02T00:54:34

First, find the x value of the vertex with the following formula:

#x_v=(-b)/(2a)#

In your function, the values are:

#a=-1#
#b=-6#
#c=-5#

Plugging those values:
#x_v=(-(-6))/(2(-1))=6/(-2)=-3#

Now you do #f(x_v)#, which is equal to the y value of the vertex (#y_v#):
#f(x_v)=-(-3)^2-6(-3)-5#
#f(x_v)=-9-(-18)-5#
#f(x_v)=4#

Your vertex is
#(x_v,y_v)#
#(-3,4)#