First of all, our general evaluation domain and definition domain are all transformed from known kinds of functions.

For example, the function y = x 2 has a domain from negative infinity to positive infinity, and the range y & gt=0. This is equivalent to what we know.

As the title suggests, y = 1/(x 2+3) is not a known function type. Then we use substitution to convert it into a familiar type.

Settings:

t=x^2+3………………( 1)

Then the original function becomes

y = 1/t …………( 2)

These two functions are obviously well-known functions. In this way, the original function becomes two well-known function types, and the value range of the original function can be obtained by using the knowledge of the relevant definition range of these two function types.