a3=a1*q^2=1又1/2=3/2a1=3/(2q^2)s3=a1+a1*q+3/2=4又1/2=9/2a1+a1q=33/(2q^2)+3/(2q)=33+3q=6q^22q^2-q-1=0(2q+1)(q-1)=0q=-1/2或a=1q=-1/2时,a1=3/(1/2)=6q=1时,a1=3/2