How do you find the axis of symmetry in the quadratic equation x²+4x+4=0

The equation of a parabola is y=a (x-p) ^2+q, where (p, q) are the coordinates of the vertex. The value of p will be your axis of symmetry.

(x+2) ^2=0

In order for 0=0

x=-2

So your axis of symmetry is x=-2