a2=a1a3
所以a²+4a+4=3a²+2a
a²-a-2=0
a=2,a=-1
a=2
则q=)a+2)/a=2
an=2^n
a=-1
则q=(a+2)/a=-1
所以
an=2*(-1)^(n-1)
已知等比数列An的前3项依次为a,a+2,3a+2(1)求a的值(2)求数列An的通项公式要有过程
已知等比数列An的前3项依次为a,a+2,3a+2(1)求a的值(2)求数列An的通项公式要有过程
数学人气:220 ℃时间:2020-05-21 02:19:20
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