-In fact, functional problems are not as terrible as we realize. The premise of solving the function problem is that you are sensitive enough to the known conditions in the function problem and can understand the hidden deep information.

For example, in this question, F(X) is a quadratic function, and f(x)+g(x) is odd function.

So how can we be sensitive?

Be sensitive and do enough questions, but just doing them is not enough.

What you have to do is to do the function problem purposefully. Concentrate on the function for a period of time, record the first step of each function problem (I call it the knife edge), make a simple record, and scan it at noon every day.

After about half a month, you will find that the function problem is not so difficult.

Be a willing heart, everything is a cloud.