这道题怎么做,可以详细点吗?
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a1(1+q+q^2) = 9/2
a1q^2 = 3/2
两式相除 1+q+q^2 = 3q^2
2q^2-q-1 = 0, (q-1)(2q+1) = 0
q = 1 , a1 = 3/2, S10 = 10a1 = 15
或缺基 q = -1/2 ,a1 = 6, S10 = a1(1-q^10)/拿扮丛(1-q) = 6(-1/2)^9 = 4-1/消樱2^8 = 1023/256
a1q^2 = 3/2
两式相除 1+q+q^2 = 3q^2
2q^2-q-1 = 0, (q-1)(2q+1) = 0
q = 1 , a1 = 3/2, S10 = 10a1 = 15
或缺基 q = -1/2 ,a1 = 6, S10 = a1(1-q^10)/拿扮丛(1-q) = 6(-1/2)^9 = 4-1/消樱2^8 = 1023/256
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