等比数列{an}的a1=5,a100=150,则a5*a100等于?
问题描述:
等比数列{an}的a1=5,a100=150,则a5*a100等于?
答
a100=a1*q^99=150
q^99=30
a5*a100=a1*q^4*a100=5*150*q^4