해결방법 - 기하 수열

수열의 일반 형식을 찾으려면, 첫 번째 항: $$a=4$$과 공비: $$r=11.25$$을 기하급수 공식에 대입합니다:

$$a_1=4$$

$$a_2=a_1·r^{n-1}=4\cdot {11.25}^{2-1}=4\cdot {11.25}^1=4\cdot 11.25=45$$

$$a_3=a_1·r^{n-1}=4\cdot {11.25}^{3-1}=4\cdot {11.25}^2=4\cdot 126.5625=506.25$$

$$a_4=a_1·r^{n-1}=4\cdot {11.25}^{4-1}=4\cdot {11.25}^3=4\cdot 1423.828125=5695.3125$$

$$a_5=a_1·r^{n-1}=4\cdot {11.25}^{5-1}=4\cdot {11.25}^4=4\cdot 16018.06640625=64072.265625$$

$$a_6=a_1·r^{n-1}=4\cdot {11.25}^{6-1}=4\cdot {11.25}^5=4\cdot 180203.2470703125=720812.98828125$$

$$a_7=a_1·r^{n-1}=4\cdot {11.25}^{7-1}=4\cdot {11.25}^6=4\cdot 2027286.5295410156=8109146.1181640625$$

$$a_8=a_1·r^{n-1}=4\cdot {11.25}^{8-1}=4\cdot {11.25}^7=4\cdot 22806973.457336426=91227893.8293457$$

$$a_9=a_1·r^{n-1}=4\cdot {11.25}^{9-1}=4\cdot {11.25}^8=4\cdot 256578451.3950348=1026313805.5801392$$

$$a_{10}=a_1·r^{n-1}=4\cdot {11.25}^{10-1}=4\cdot {11.25}^9=4\cdot 2886507578.1941414=11546030312.776566$$