সমাধান - জ্যামিতিক ধারা

সিরিজের সাধারণ রূপ খুঁজে পেতে, প্রথম পদ: $$a=85$$ এবং সাধারণ অনুপাত: $$r=0.8$$ জ্যামিতিক সিরিজের সূত্রে প্লাগ করুন:

$$a_1=85$$

$$a_2=a_1·r^{n-1}=85\cdot {0.8}^{2-1}=85\cdot {0.8}^1=85\cdot 0.8=68$$

$$a_3=a_1·r^{n-1}=85\cdot {0.8}^{3-1}=85\cdot {0.8}^2=85\cdot 0.6400000000000001=54.40000000000001$$

$$a_4=a_1·r^{n-1}=85\cdot {0.8}^{4-1}=85\cdot {0.8}^3=85\cdot 0.5120000000000001=43.52000000000001$$

$$a_5=a_1·r^{n-1}=85\cdot {0.8}^{5-1}=85\cdot {0.8}^4=85\cdot 0.4096000000000001=34.81600000000001$$

$$a_6=a_1·r^{n-1}=85\cdot {0.8}^{6-1}=85\cdot {0.8}^5=85\cdot 0.3276800000000001=27.852800000000006$$

$$a_7=a_1·r^{n-1}=85\cdot {0.8}^{7-1}=85\cdot {0.8}^6=85\cdot 0.2621440000000001=22.28224000000001$$

$$a_8=a_1·r^{n-1}=85\cdot {0.8}^{8-1}=85\cdot {0.8}^7=85\cdot 0.20971520000000007=17.825792000000007$$

$$a_9=a_1·r^{n-1}=85\cdot {0.8}^{9-1}=85\cdot {0.8}^8=85\cdot 0.1677721600000001=14.260633600000007$$

$$a_{10}=a_1·r^{n-1}=85\cdot {0.8}^{10-1}=85\cdot {0.8}^9=85\cdot 0.13421772800000006=11.408506880000006$$