Sequences and Series

Sequence



ေထာα€€္α€™ွာေပးထားတဲ့ α€€ိα€”္းတန္းေα€œးα€€ို ေα€œ့α€œာαΎα€€α€Š့္α€›ေထာင္။



1,4,9,16,25,...



ထခုα€€ိα€”္းတန္းα€™ွာပါ၀င္တဲ့ α€€ိα€”္းα€œံုးေတြα€Ÿာ ေα€›းခ်င္α€žα€œို ေα€›းထားျခင္း (random) α€™α€Ÿုတ္ပါα€˜ူး။ α€€ိα€”္းα€œံုးေတြ ေျပာင္းα€œဲα€™ႈα€™ွာ α€…α€”α€…္တစ္ခု (α€α€”α€Š္းေျပာရရင္ function တစ္ခု) ထရ ေျပာင္းα€œဲα€žြားတာပါ။ α€’ါα€€ို functional notation α€”ဲα‚”ေျပာα€›α€™α€š္ဆိုရင္...



f(1) = 1 = 12

f(2) = 4 = 22

f(3) = 9 = 32

f(4) = 16 = 42

f(5) = 25 = 52 α€œို႔ဆိုႏိုင္တာေပါ။့



α€’ါα€€ိုαΎα€€α€Š့္ျခင္းထားျဖင့္ function α€›ဲ့ Domain α€Ÿာ {1,2,3,4,5,...n}=the set of natural numbers ဆိုရပါα€™α€š္။ α€’ါဆိုရင္ ထထက္ပါေျပာင္းα€œဲα€™ႈα€€ို αΎα€€α€Š့္α€›ံုα€”ဲα‚” function α€›ဲ့ general formula α€€ို α€‘α€œြα€š္တကူ ေျပာႏိုင္ပါၿပီ။

f(n) = n2 ေပါ့...။



α€’ါေၾကာင့္ sequence ဆိုတာα€Ÿာ special function α€œို႔ဆိုႏိုင္ၿပီး α€žူα€›ဲ့ domain α€€ေတာ့ ထၿမဲတမ္း α€žα€˜ာ၀ကိα€”္း α€™်ား ပါ၀င္ေα€žာထစု (the set of natural numbers) ျα€–α€…္ပါα€α€š္။ image ေတြα€€ိုေတာ့ α€’ီေα€”α€›ာα€™ွာ terms α€œိုα‚” ေျပာင္းα€œဲေα€αšα€•ါα€™α€š္။ ထေα€αšα€‘ေα€αš ေျပာင္းα€œဲα€™ႈα€”ဲ႔ထတူ α€‘α€žံုးျပဳα€™α€š့္ symbols ေတြα€€ိုα€œα€Š္း ေျပာင္းα€œα€Š္း α€žα€္α€™ွတ္ပါα€α€š္။ ထထက္α€™ွာေပးထားတဲ့ α€€ိα€”္းα€œံုးေတြα€€ို ထခုα€œိုေα€αšေα€αš α€žα€္α€™ွတ္ပါα€™α€š္။

first term =u1 =1
second term=u2=4
third term =u3 =9
fourth term =u4 =16
fifth term =u5 =25
- - - - - - - - - - - - - - - -
nth term =un=n2

α€’ီေα€”α€›ာα€™ွာ nth term α€€ို general term α€žိုα‚”α€™α€Ÿုတ္ general formula α€œို႔ဆိုႏိုင္ပါα€α€š္။ α€’ါေၾကာင့္ sequence α€€ို ထခုα€œို definition α€–ြင့္ဆိုႏိုင္ပါα€α€š္။



Sequence

A sequence is a function whose domain is either the set of all or part of natural numbers. The values (images) of function are called terms .



Example 1

Find the first four terms of the sequence defined by un = 3n - 5.



http://i627.photobucket.com/albums/tt352/Thu-Rein/template/th_bluearrow.gifSolution

un = 3n - 5

u1 = 3(1) - 5 =-2

u2 = 3(2) - 5 = 1

u3 = 3(3) - 5 = 4

u4 = 3(4) - 5 = 7

Therefore the fist four terms are -2, 1, 4, 7.



Exercises

Find the first four terms of the sequence defined by

(a) un = 2n + 3(b) un = 3n2 - 2(c) un = 4n2+ 3n - 5
Example2

Which term of the sequence defined by un = 4n - 23 is 25?



http://i627.photobucket.com/albums/tt352/Thu-Rein/template/th_bluearrow.gifSolution

un = 4n - 23

Let the nth term be 25.

Therefore un = 25

4n - 23 = 25

4n = 48

n = 12

Therefore the 12th term is 25.
α€…ာဖတ်α€žူ၏ ထမြင်α€€ို α€œေးα€…ားα€…ွာα€…ောင့်α€™ျှော်α€œျα€€်!

Post a Comment

To be published, comments must be reviewed by the administrator *

Previous Post Next Post
πŸ’¬ 1
TM
Target Mathematics
Usually replies instantly
TM
Target Mathematics α€™ှ α€€ူα€Šီα€›α€”် α€‘α€žα€„့်α€›ှိပါα€α€š်။ α€˜ာα€™ျား α€žိα€›ှိချင်ပါα€žα€œဲ။ Target Mathematics Facebook Page α€™ှာα€œဲ တိုα€€်α€›ိုα€€် α€™ေးα€™ြα€”်းα€”ိုင်ပါα€α€š်