(2n-3)^20(3n+2)^30/(5n+5)^50
=(2-3/n)^20/n^20 * (3+2/n)^30*/n^30 / (5+5/n)^50/n^50
=(2-3/n)^20(3+2/n)^30/(5+5/n)^50
所以
lim(n→∞)(2n-3)^20(3n+2)^30/(5n+5)^50
=lim(n→∞)(2-3/n)^20(3+2/n)^30/(5+5/n)^50
=2^20*3^30/5^50