Diketahui U5= 42 dan U8=15 tentukan deret ke14​

U5 = a + 4b = 42

U8 = a + 7b = 15

—————– –

-3b = 27

b = 27/-3= -9

a + 4b = 42

a + 4(-9)= 42

a + (-36) = 42

a = 78

U14 = a + 13b

= 78 + 13(-9)

= 78 + (-117)

= -39