Ketahui U2 + U4 = 12 dan U3 + U5 = 16 maka suku ke-7 barisan itu adalah

U2 + U4 = 12
U3 + U5 = 16
U2 = a + b
u4 = a + 3b
u3 = a + 2b
u5 = a + 4b

a + 2b + a + 4b = 16
2a + 6b = 16

a + b + a + 3b = 12
2a + 4b = 12

2a + 6b = 16
2a + 4b = 12
—————– –
0 + 2b = 4
b = 2
2a + 6b = 16
2a + 6.2 = 16
2a + 12 = 16
2a = 16 – 12
2a = 4
a = 2

u7 = a + 6b = 2 + 6.2 = 2 + 12 = 14
u7 = 14