yang bisa, tolong bantu ya..dari no 1-4

2.A=3 b=3
Sn = n/2 (2a + (n-1) b)
165 = n/2 (2.3+ (n-1) 3)
165 = n/2 (6+3n-3)
165 = n/2 (3+3n)
330 = 3n^2 + 3n
3n^2 + 3n - 330= 0
n^2 + n - 110= 0
(n-10) (n+11)
n=10 V n=-11
a. jawaban banyak suku =10

U10= 3+(10-1)3
= 3+9.3
= 3+27
= 30
b. suku terakhirnya 30
3.Bil bulat antara 1 - 50 --> 2, 3, 4, ... , 49
a = 2
b = 1
Un = 49
Un = a+(n-1)b
49 = 2+(n-1)1
49 = 2+n-1
n = 49-2+1
n = 48

Sn = n/2 (2a+(n-1)b)
S48 = 48/2 (2.2+47.1)
= 24 (4+47)
= 24 x 51
= 1224

bil bulat antara 1 - 50 yg habis dibagi 3 --> 3, 6, 9, ... , 48
a = 3
b = 3
Un = 48
Un = a+(n-1)b
48 = 3+(n-1)3
48 = 3+3n-3
3n = 48
n = 16

Sn = n/2 (2a+(n-1)b)
S16 = 16/2 (2.3+15.3)
= 8 (6+45)
= 8 x 51
= 408

jumlah semua bul bulat antara 1 - 50 yg tidak habis dibagi 3
= 1224 - 408
= 816