সমাধান - জ্যামিতিক ধারা

সিরিজের সাধারণ রূপ খুঁজে পেতে, প্রথম পদ: $$a=2,100$$ এবং সাধারণ অনুপাত: $$r=0.7$$ জ্যামিতিক সিরিজের সূত্রে প্লাগ করুন:

$$a_1=2100$$

$$a_2=a_1·r^{n-1}=2100\cdot {0.7}^{2-1}=2100\cdot {0.7}^1=2100\cdot 0.7=1470$$

$$a_3=a_1·r^{n-1}=2100\cdot {0.7}^{3-1}=2100\cdot {0.7}^2=2100\cdot 0.48999999999999994=1028.9999999999998$$

$$a_4=a_1·r^{n-1}=2100\cdot {0.7}^{4-1}=2100\cdot {0.7}^3=2100\cdot 0.3429999999999999=720.2999999999998$$

$$a_5=a_1·r^{n-1}=2100\cdot {0.7}^{5-1}=2100\cdot {0.7}^4=2100\cdot 0.24009999999999995=504.2099999999999$$

$$a_6=a_1·r^{n-1}=2100\cdot {0.7}^{6-1}=2100\cdot {0.7}^5=2100\cdot 0.16806999999999994=352.9469999999999$$

$$a_7=a_1·r^{n-1}=2100\cdot {0.7}^{7-1}=2100\cdot {0.7}^6=2100\cdot 0.11764899999999996=247.06289999999993$$

$$a_8=a_1·r^{n-1}=2100\cdot {0.7}^{8-1}=2100\cdot {0.7}^7=2100\cdot 0.08235429999999996=172.9440299999999$$

$$a_9=a_1·r^{n-1}=2100\cdot {0.7}^{9-1}=2100\cdot {0.7}^8=2100\cdot 0.05764800999999997=121.06082099999995$$

$$a_{10}=a_1·r^{n-1}=2100\cdot {0.7}^{10-1}=2100\cdot {0.7}^9=2100\cdot 0.04035360699999998=84.74257469999995$$