R8 # Persiapan UN SMP 2017 # Diutamakan siswa - siswi SMP. Gunakan cara / langkah yang baik dan benar. (x - 1), (x - 3/2), (x - 7/4) adalah 3 suku pertama deret

( x - 1 ) , ( x - 3/2) , (x - 7/4)
Rumus : U1 x U3 = (U2)² <-- a x ar² = a²r²= (ar)²= (U2)²

(x - 1)(x - 7/4) = (x - 3/2)(x - 3/2)

1 = 4/4

x² - 7/4 x - (4/4)x + 7/4 = x²- 3/2 x - 3/2x + 9/4
------------------------------------------------- ×4
4x² - 7x - 4x + 7 = 4x² - 6x - 6x + 9
4x² - 11x + 7 = 4x² - 12x + 9

Coret 4x²
-11x + 7 = -12x + 9
-11x + 12x = 9 - 7
x = 2

Barisannya
( 2 - 1) , (2 - 3/2) , (2 - 7/4) --> (2 - 1) , (4/2 - 3/2 ) , (8/4 - 7/4)
--> 1 , 1/2 , 1/4
a = 1
r = U2 / U1 = (1/2 )/1 = 1/2

Un = ar^(n-1)
U10 = 1 . (1/2) ^ (10-1)
= (1/2)^9
= 1 / (2^9)
= 1/512

Rasio : (x-3/2) / (x-1) = (x-7/4) / (x-3/2) =
(x-3/2)^2 = (x-1) (x-7/4)
x^2 - 3x + 9/4 = x^2 - 11/4x + 7/4
-3x - (11/4)x = (7/4) - (9/4)
(-23/4)x = (-1/2)
x = (-1/2) / (-23/4)
x = (-1/2)*(-4/23)
x = 4/46
x = 2/23

u1 = (2/23) - 1 = (-21/23)
U2 = (2/23)-(3/2) = (4-69)/46 = (-65/46)
rasio.=
(-65/46) / (-21/23) =
(-65/46)*(23/-21) = (-65/-42) = 65/42

U10 = ar^9 = (-21/23).(65/42)^9