It is known that the parabola y = x ^ 2 + 2x + m intersects with X axis at two points AB, and the equation of a circle with diameter AB is obtained

It is known that the parabola y = x ^ 2 + 2x + m intersects with X axis at two points AB, and the equation of a circle with diameter AB is obtained

Axis of symmetry x = - 1
So the center of the circle (- 1,0)
Weida theorem X1 + x2 = - 2
x1x2=m
Then AB ^ 2 = | x1-x2 | ^ 2
=(x1+x2)^2-4x1x2
=4-4m
Then R ^ 2 = AB ^ 2 / 4 = 1-m
So (x + 1) ^ 2 + y ^ 2 = 1-m, where M