Question

No.6 gimana cara mengerjakannya?

Answer 1

Un = a + (n-1)b

U4 = a + (4-1)b
= a + 3b
a + 3b = 19

U7 = a + (7-1)b
= a + 6b
a + 6b = 37

a + 6b = 37
a + 3b = 19_-
3b = 18
b = 18 / 3
b = 6

a + 3b = 19
a + 3(6) = 19
a + 18 = 19
a = 19 - 18
a = 1

Sn = 1/2 n (2a + (n-1)b)
S24 = 1/2 . 24 (2.1 + (24-1)6)
= 12 (2 + (23)(6))
= 12 (2 + 138)
= 12 (140)
= 1680

Answer 2

U4 = 19 = a+3b
U7 = 37= a+6b -
= 18 a+3b
= 18 : 3
b= 6
U4 = 19 = a+3(6)
=19 = a+18
a = 19-18
a = 1

S24 = n/2 + (2a +(n-1)b)
= 24/2 + (2(1) + 23(6)
= 12 + (2+ 138)
= 12 (140)
= 1680