y=(x+4)(x+2)
This is the equation for a parabola that opens upward. It crosses
the x-axis at two points. At each of those points, the y value is zero.
That makes the equation 0=(x+4)(x+2)
One or both of the terms on the right side must equal zero to get
a zero result.
x + 4 = 0
x = -4
x + 2 = 0
x = -2
This tells us that the parabola crosses the x-axis at
(-4,0) and at (-2,0)