We call functions that do not give specific analytical formulas abstract functions. To put it simply, an abstract function is composed of only f(x) and has no function expression. For example, f(x·y)=f(x) f(y), to find f(1)=? For general abstract functions, you can Let x=y=1, or -1 or 0, and you can get what you want. Of course, this also depends on what the specific question requires. You can also let x=1, y=0. Wait, there are many, usually The numbers are generally 1, -1, and 0. Here f(x·y)=f(x)f(y), to find f(1)=? is an abstract function, just let x=y =1, we have f(1)=f(1) f(1), we get f(1)=0 Finally, if you have a very good understanding of the functions you learned in high school, you will know that in fact, these abstract functions It is the property of the function you have learned. Just like the example just mentioned, if you can see at a glance that the function f(x) is a logarithmic function...and so on
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