what is the vertex of f(x)=-2x^2-4x

f(x)=-2x^2-4x

Without using Calculus, we can find the x coordinate of the vertex by ... x = -b/2a......where, in this case, b= -4 and a = -2.....so we have

x = -b/2a  = -(-4) / 2(-2) = 4 / -4  = -1

Now, to find the "y" coordinate of the vertex, just put -1 back into the function for each "x" and evalute the result......

So you will have.... -2(-1)^2  - 4(-1)   =  'y"

Can you take it from here???