jika (a+2), (a-1), (a-7),.... membentuk barisan geometri , maka rasionya adalah.. a.-5 b.-2 c.-1/2 d.1/2 e.2

Saya bantu jawab ya.

Rasio = U2/U1 = U3/U2 = U4/U3 = ... = U(n)/U(n-1)

U1 = a+2
U2 = a-1
U3 = a-7

a-7/a-1 = a-1/a+2
(a-7) × (a+2) = (a-1) × (a-1)
a^2 + 2a - 7a - 14 = a^2 - a - a + 1
2a - 7a - 14 = -2a + 1
-5a + 2a = 14 + 1
-3a = 15
a = 15 ÷ -3
a = -5

Substitusikan :

U1 = a + 2 = -5 + 2 = -3
U2 = a - 1 = -5 - 1 = -6
U3 = a - 7 = -5 - 7 = -12

r = U2 ÷ U1 = U3 ÷ U2
r = -6 ÷ -3 = -12 ÷ -6
r = 2

rasio = 2