lim[(5n^2-7n^2+1)/(n-1)^2]n→∞

lim(n→∞)[(5n^2-7n^2+1)/(n-1)^2]
=lim(n→∞)(-2n^2+1)/(n^2-2n+1)
=lim(n→∞)(-2+1/n^2)/(1-2/n+1/n^2)
=-2/1
=-2
【若题目中分子-7n^2写错,是-7n的话】
lim(n→∞)[(5n^2-7n+1)/(n-1)^2]
=lim(n→∞)(5n^2-7n+1)/(n^2-2n+1)
=lim(n→∞)(5-7/n+1/n^2)/(1-2/n+1/n^2)
=5/1
=5
如果不懂,祝学习愉快!

5n^2-7n^2=-2n^2
lim[(5n^2-7n^2+1)/(n-1)^2]n→∞
=-2
是"lim[(5n^2-7n+1)/(n-1)^2]n→∞"的话
=5