diketahui baris aritmatika -7,-4,-1,2,.. suku ke 40 barisan tersebut adalah

a = U1 = -7

b = U2 - U1
b = -4 - (-7)
b = -4 + 7
b = 3

U40 = a + (n - 1) . b
U40 = -7 + (40 - 1) . 3
U40 = -7 + 39 . 3
U40 = -7 + 117
U40 = 110

U1=a=-7
b = -4-(-7) = 3

Un = a + (n-1)b
U40 = -7 + (40-1)3
U40 = 110