解由f(x+1)=[1+f(x)]/[1-f(x)]
得f(x+2)=[1+f(x+1)]/[1-f(x+1)]
=[1+[1+f(x)]/[1-f(x)]]/[1-[1+f(x)]/[1-f(x)]]
=2/-2f(x)
即f(x+2)=-1/f(x)
故f(x+4)=f(x+2+2)=-1/f(x+2)=-1/[-/f(x)]=f(x)
故f(x+4)=f(x)
故T=4
又由f(1)=1
则f(-3)=f(-3+4)=f(1)=1
解由f(x+1)=[1+f(x)]/[1-f(x)]
得f(x+2)=[1+f(x+1)]/[1-f(x+1)]
=[1+[1+f(x)]/[1-f(x)]]/[1-[1+f(x)]/[1-f(x)]]
=2/-2f(x)
即f(x+2)=-1/f(x)
故f(x+4)=f(x+2+2)=-1/f(x+2)=-1/[-/f(x)]=f(x)
故f(x+4)=f(x)
故T=4
又由f(1)=1
则f(-3)=f(-3+4)=f(1)=1