pada suatu barisan geometri diketahui: U1+U3=25 dan U5=81/16. Tentukan U2

Langsung aja y

U1 + U3 = 25
a + a + 2b = 25
2a + 2b = 25
a + b = 25/2

U5 = a + 4b = 81/16

a + b = 25/2
a + 4b = 81/16
___________-
-3b = 119/16
b = 119/16 : -3
b = - 119/48

a + b = 25/2
a = 25/2 + 119/48
a = 600/48 + 119/48
a = 719/48

U2 = a + b
U2 = 719/48 + (-119/48)
U2 = 719/48 - 119/48
U2 = 600/48
U2 = 25/2

atau cara singkat aja

U2 = a + b

maka
U1 + U3 = 25
a + a + 2b = 25
2a + 2b = 25
2(a+b) = 25
a + b = 25/2

jadi U2 = 25/2

Semoga berguna +_+