The second question: if we set the slope, we can find point A and point B by connecting the equations, and then. . . Basically, I want to die.
Using symmetric attributes is the best idea. Find the intersection point B' between the extension line of AF 1 and the ellipse, and the abscissa of point B' and point b is the inverse number.
The value of x 1-x2 can be obtained by replacing the known equation with the focal radius formula.
Then connect the straight line AB' with the elliptic equation, construct an equation with Vieta theorem, and get the result.
Try it yourself.