lim,x趋于无穷,((根号下x的平方+1)-(根号下x的平方-2))
=lim,x趋于无穷,((√x^2+1)-(√x^2-2))((√x^2+1)+(√x^2-2))/((√x^2+1)+(√x^2-2))
=lim,x趋于无穷,3/((√x^2+1)+(√x^2-2))
=0
lim,x趋于无穷,((根号下x的平方+1)-(根号下x的平方-2))
=lim,x趋于无穷,((√x^2+1)-(√x^2-2))((√x^2+1)+(√x^2-2))/((√x^2+1)+(√x^2-2))
=lim,x趋于无穷,3/((√x^2+1)+(√x^2-2))
=0