∵f(x-1/x)=(x+1/x)(x+1/x)==>f(x-1/x)=x²+1/x²+2==>f(x-1/x)=x²+1/x²-2+4==>f(x-1/x)=(x-1/x)²+4∴f(x)=x²+4故f(x+1)=(x+1)²+4=x²+2x+5.