[根号(x+1)+根号(x-1)]分之[根号(x+1)-根号(x-1)]+[根号(x+1)-根号(x-1)]分之[根号(x+1)+根号(x-1)]
=[√(x+1)-√(x-1)]/[√(x+1)+√(x-1)]+[√(x+1)+√(x-1)]/[√(x+1)-√(x-1)]
={[√(x+1)-√(x-1)][√(x+1)-√(x-1)]+[√(x+1)+√(x-1)][√(x+1)+√(x-1)]}/[√(x+1)-√(x-1)][√(x+1)+√(x-1)]
=[x+1-2√(x+1)(x-1)+x-1+x+1+2√(x+1)(x-1)+x-1]/(x+1-x+1)
=4x/2
=2x
=2*(√5)/2
=√5