Origin o (0 0,0), a (0, 1), b (2 2,2), c (x x,0).

Then the two line segments mentioned above are AC and BC, and point C is on the X axis.

Find the minimum length of CA+CB.

(If A and B are on both sides, then directly connect AB, and the intersection point with X axis is point C, and the line segment between two points is the shortest). Both A and B are above X axis, and B is symmetrical about X axis by using the principle of small mirror image, and the intersection point connecting AB' and X axis is point C, because CB' = CB is a constant, or the line segment between two points is the shortest. (Making a point a' around the X axis has the same effect.)

Just draw it yourself. Just try it.

Of course, taking a point in front makes it A(0,-1) and B (2 2,2); A(0, 1) and B(2, -2) look directly at the contents in brackets above. If A(0,-1) and B(2, -2), it is the same as writing a lot.