1Tentukan nilai dari A. 2+7+12+....+297 B. 30+26+22+...+2 2. Tentukan x jika A. 100+96+92+....+x=0 B. 1+4+7+....+x=835 Tolongg dibantuu ya guyss >< tq

1•
A. Barisan Aritmatika
2 + 7 + 12 + ... + 297
a = 2
b = 5
n = (297 - 2)/5 + 1 = 60

2 + 7 + ... + 297 = S60

S60 = (n/2)(a + Un)
S60 = 30(2 + 297)
S60 = 8970

B. Barisan Aritmatika
30 + 26 + 22 + ... + 2 = S8
a = 30
b = -4
n = (2 - 30)/-4 + 1 = 8

S8 = (4)(30 + 2) = 128

2•
100 + 96 + 92 + ... + x = 0
a = 100
b = -4

Sn = (n/2)(2a + (n - 1)b)
0 = n(200 + (n - 1)(-4))
0 = 204n - 4n²
O = 4n(51 - n)
n = 51

x = U51 = a + 50b = 100 - 200 = -100