The first one: the symmetry axis of f(a+x)=f(b-x) is x=(a+b)/2. Note that this is an axisymmetric function image, and it is an image. We must first know a relationship: if f(a+x)=f(a-x), then it is symmetrical about x=a, which can be realized by making y = a+x, then x=y-a, then f(y)=f[(b+a)-y], so the symmetry axis is x = (a). Second, the symmetry axis of function y=f(a+x) and function y=f(b-x) is x=(b-a)/2. Note that this is an image of two functions. In this way, the shape of the image does not change, but is symmetrical, but the symmetry axis is not the Y axis, but the middle line between x=b and x=-a, so the middle position is x=(b-a)/2.