1 证明：由题意得,当x1=x2=0时f(x1+x2)=f(0+0)=f(0),f(x1)*f(x2)=f(0)*f(0)=f(0)^2由f(x1+x2)=f(x1)*f(x2)得f(0)=f(0)^2又因为函数y=f(x)恒不为零,故得f(0)=1故得f(0)=f(x-x)=f(x+(-x))=f(x)*f(-x)=1,即 f(-x)=1/f(x...