I am also a senior one this year. The following is just my opinion (for reference only).

1。 With regard to the symmetry of y=x, like the simple function you gave, first draw a picture to find the intersection point with the coordinate axis, and then symmetric the intersection point with respect to y=x to get two new point coordinates, and then you can find f(x). As for the domain, just look at the picture.

2. Number

Draw a picture first. According to the meaning of the question, two equations can be listed and solved. My answer is-1, +∞)

I'm not good at it either. I hope I can help you.