设{an}公差为d,数列各项不为0,an≠0
a4-2a7²+3a8=0
(a7-3d)-2a7²+3(a7+d)=0
整理,得a7²-2a7=0
a7(a7-2)=0
an≠0 a7≠0 a7=2
b7=a7=2
b2b8b11=(b7/q^5)(b7q)(b7q^4)=b7³=2³=8
设{an}公差为d,数列各项不为0,an≠0
a4-2a7²+3a8=0
(a7-3d)-2a7²+3(a7+d)=0
整理,得a7²-2a7=0
a7(a7-2)=0
an≠0 a7≠0 a7=2
b7=a7=2
b2b8b11=(b7/q^5)(b7q)(b7q^4)=b7³=2³=8