我们已经学习过一元一次方程、一元二次方程、三角方程、对数方程、指数方程等,这些方程的一个共同特点是有确定的函数.另外,我们也研究过在x∈D上有f(-x)=f(x),f(-x)=-f(x),f(x+T)=f(x)(T≠0).这些等式中,都是以函数为未知数,像这种含有未知函数的等式,叫做函数方程,使函数 We have studied unary first-order equations, unary quadratic equations, trigonometric equations, logarithmic equations, exponential equations, etc. One common feature of these equations is that there are deterministic functions. In addition, we have also studied f() on x∈D. -x)=f(x),f(-x)=-f(x),f(x+T)=f(x)(T≠0). In these equations, functions are unknown, An equation like this containing an unknown function, called a function equation, makes the function