Analysis: It is proved that the symmetry axis of abstract function f(a-x)= abstract function f(a+x) is X=a axis.

That is to say, the images on the left and right sides of the X=a axis are equal (that is, the Y values from the same distance to the X=a axis are equal, which is a property).

Syndrome: let the abscissa a a-x, a+X.

∴?a-(a-x) ? = ? x ?

(a+X)é=é-Xé

Abstract function f(a-x)= abstract function f(a+x)

∴ abstract function f(a-x)= the symmetry axis of abstract function f(a+x) is X=a axis.

Note: the conclusion of the formula is that when f(a-x)=f(b+x), the symmetry axis X= 1/2*(a-x+b+x).

You can also try to prove it.