no. 2-4 saja jawab tepat

jawab

2) tiga suku berikutnya
1, 5, 9
(bertambah tetap 4)
1, 5, 9, (13), (17), (21)

b)
4, 16, 36, 64,..
(2²), (4²), (6²), (8²), (10²), (12²) , (14²) 
= 4, 16, 36, 64, 100, 144, 196

(3)
a.  1+3+..+25 , un = 2n -1
25 = 2n -1
n = 13

13
Σ  2k- 1
k= 1

b. 2 + 4 +...50 , un= 2n
2n = 50 
n= 25

25
Σ 2k
k= 1

c. 1/(1+1) + 2/(2+1) + 3/(3+1) +...+ (75/76), un= n/(n+1)
n = 75

75
Σ  k/(k+1)
k = 1

(4)
a.
uk = 4 - 2k
k = (1,2,3,4,5)
k =1 , uk = 2
k = 2 , uk = 0
k = 3, uk = -2
k = 4, uk = -4
k = 5 , uk = -6
jumlahkan semua  = -10

b. 
uk = 1/(k+2)
k = (1,2,..,10)
k = 1 , uk = 1/3
k = 2 , uk = 1/4
nilai = 1/3 + 1/4 + 1/5 + ...+ 1/12
1/3 + 1/5 + 1/7 +1/9 +1/11 =  7/8
1/4 + 1/6 + 1/8 + 1/10 + 1/12 = 29/40
jumlah  7/8 + 29/40 = 64/40= 8/5

4c
uk = k(k+1)(k+2)
k = 1,2,3,4,5,6
k = 1, uk = 1(2)(3) = 6
k = 2 , uk = 2(3)(4)= 24
k = 3 ,uk= 3(4)(5) = 60
k = 4, uk = 4(5)(6)= 120
k= 5, uk = 5(6)(7) = 210
k = 6, uk = 6(7)(8)= 336
jumlahkan = 756