Question

para kakak brainly.. mohon bantu soal ini dengan pake cara.. kalo dah di jawab nanti aku kasih mahkota...

Answer 1

15)
a = -98
b = -95-(-98) = 3
U50 = -98 + 49x3 = 147-98 = 49
S50 = 50 x (-98+49)/2
= 50x(-49)/2
= -1.225

16)
u4 = 110
u9 = 150
b = (150-110)/(9-4) = 40/5 = 8
u4 = a + 3b
110 = a + 3x8
a = 110 - 24 = 86

U30 = 86 + 29x8 = 86 + 232 = 318

17)
u5 = 22
u12 = 57
b = (57-22)/(12-5) = 35/7 = 5
u5 = a + 4b
22 = a + 4x5
a = 22 - 20
a = 2
U14 = 2 + 13x5 = 2 + 65 = 67

S14 = 14/2 x (2 + 67) = 7 x 69 = 483

18)
Un = 3n - 5
U1 = 3(1) -5 = -2
Sn = n/2 x ( -2 + 3n -5)
Sn = n x (3n -7)/2
Sn = n/2 x (3n - 7)

19)
3,4,6,9,....
2 suku berikutnya = (9+4) , (9+4+5) = 13 , 18

20)
a = 27
r = 9/27 = ⅓

Un = 27 x ⅓^(n-1)
Un = 3³ x 3^(1-n)
Un = 3^(4-n)