[질문] 등비수열 a2더하기a4는810이고 a5더하기a7은 30일때 a10은?어떻게구해요ㅠ

첫째항a,공비r일때a2+a4=ar+ar^3=810,a5+a7=ar^4+ar^6=30,즉810*r^3=30,r^3=1/27,r=1/3,a2+a4=a/3+a/27=10a/27=810,a=81*27=3^7,a10=ar^9=3^7*(1/3)^9=1/9