等差数列{an}.a1+a7=22.a4+a10=40求公差d

问题描述:

等差数列{an}.a1+a7=22.a4+a10=40求公差d

a1+a7=2a4=22,则:a4=11.a4+a10=40,得:a10=29,a10-a4=6d=18,得:d=3