Question

等比数列{An}的前n项和SN=3X2^n+C 则常数C=

Answer 1

a1=s1=6+c

a2=s2-s1=12+c-6-c=6

a3=s3-s2=24+c-12-c=12.

得公比为2,a1=3,得c=-3