Page 19 - Math Grade 11 (Advance)

PROEUS DARA

en= 16+6(n-l) = 16+6n-6 = 6n+ lO

n-! n-!
thmg 122:2 tl:lQIS bn = b + ~ ck = 14+ ~ (6k+ 10)
1
k =I k =I
n-!
= 14+6 ..L,k+l0(12-l) = 14+6·;zn(n-1)+10(12-1) = 3n 2 +7n+4
1
""'
k =I
0
mmg 12 = tl:lQIS b = 4 + 7 + 3 = 14 Clfi '1
1
n-l n-l
2
1
~tmg n<::2 tl:lQlS an=a +~bk=4+~(3k +7k+4)
k = l k = l
n-! n-!
2
k
k
= 4 + 3 ~ + 7 ~ + 4(n- 1)
k = l k =I
1 1
= 4 + 3 · 12(12- 1 )(2n- 1) + 7 · (12- 1 )n + 4n- 4
6 2
1 2 2 3 2
= (12-1)(7n+2n -n)+412 = (n-1)(3n+n )+4n = n +2n +n
2
3 2
an= n + 212 + n '1
0 "o C»
2. l:lrt.fiSltHlitH1 n nl::l'i.HltSMfi (an)
u u u d
1
mtl sn thtHli'iJntsfiJn (an) ~
1

n n
2
sn = ~ak = ~(k +2k +k)
3
k=l k=l

1 2 2 1 1
= :q:n (l+n) +2· n(n+1)(2n+1)+ n(n+l)
6 2
1 2
= n(n + 1 )(3n + 3n + 4 + 8n + 6)
12
1 2
= n(n + 1)(3n + lln + 10)
12

0 • t:::l1 '1:) C»
firt.fln~&l n tS~n 1, 2, 5, 12, 27, 58, 121, ... '1
1