bantu plis... besok di kumpulkan pakai cara ya... no 1-2 arimatika 3-4 geometri, bantu plis...
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1. U1 = 5
U6 = 35
Un = a + (n - 1) b
U1 = a + b = 5 .... persamaan 1
U6 = a + 5b = 35 .... persamaan 2
Eliminasi a dari persamaan 1 dan 2
a + b = 5
a + 5b = 35
_________-
-4b = -30
b = 7,5
Substitusi b ke persamaan 1
a + b = 5
a + 7,5 = 5
a = 5 - 7,5
a = -2,5
Un = a + (n - 1) b
U28 = -2,5 + (28 - 1) 7,5
U28 = -2,5 + 202,5
U28 = 200
2. U3 = 2
U6 = -7
Un = a + (n- 1) b
U3 = a + 2b = 2 .... persamaan 1
U6 = a + 5b = -7 .... persamaan 2
Eliminasi a dari persamaan 1 dan 2
U3 = a + 2b = 2
U6 = a + 5b = -7
____________-
-3b = 9
b = -3
Substitusi b ke persamaan 1
a + 2b = 2
a + 2(-3) = 2
a - 6 = 2
a = 2 + 6
a = 8
Un = a + (n - 1) b
U5 = 8 + (5 - 1) (-3)
U5 = 8 + (-12)
U5 = -96
3. a. 9, 27, 81, 243, ....
a = 9
r = 27/9 = 3
.
b. 4, 12, 36, 108, ....
a = 4
r = 12/4 = 3
.
4. U1 = 4
r = -2
[tex]un = ar ^{n - 1} \\ u1 = a \times ( - 2) ^{(1 - 1)} = 4 \\ a \times( - 1) =4 \\ a = - 4[/tex]
[tex]u8 = - 4 \times { - 2}^{ ( 8 - 1)} \\ u8 = 512[/tex]