[질문] 등비수열3,X1,X2,···Xn,27의모든항의곱이3의12제곱 n의값 공비r를구하여라

3*X1*X2*...*Xn*3^3=3*r*3*r^2*3*...*r^n*3*3^3=3^4*3^n*r^[{n(n+1)}/2]입니다^^ 27=3*r^(n+1)이므로r^(n+1)=9 3^(4+n)*9^(n/2)=3^(4+2n)=3^12즉,n=4