容易判定q≠1等比数列an,a5-a1=a1*q^4 -a1=15a4-a2=a1*q³-a1*q=6∴(q^4-1)/(q³-q)=5/2(q²+1)/q=5/22q²+2=5q2q²-5q+2=0(q-2)(2q-1)=0∴q=2或q=1/2∵a5-a1＞0∴q＞1∴q=2,a1=1∴a5=a1*q^4=16...