Jawab:
[a]  =  43
[b]  = 41
[c]  = 63
[d]  =  66
[e]  =  -18 ¾

Penjelasan:
[a] {7, 11, 15, 19}
-> Suku pertama (a) = 7
beda = 11-7 = 4
-> Beda (b) = 4
Suku ke-10 berarti
-> n = 10
Ditanya suku ke-10
Un = a+b(n-1)
U₁₀ = 7+4(10-1)
U₁₀ = 7+40-4
U₁₀ = 3+40
U₁₀ = 43
Suku ke-10 = 43
------------------------
[b] {-15, -11, -7, -3}
-> Suku pertama (a) = -15
beda = -11-(-15) = 15-11 = 4
-> Beda (b) = 4
Suku ke-15 berarti
-> n = 15
Ditanya suku ke-15
Un = a+b(n-1)
U₁₅ = -15+4(15-1)
U₁₅ = -15+60-4
U₁₅ = 41
Suku ke-15 = 41
------------------------
[c] {-5, -1, 3, 7}
-> Suku pertama (a) = -5
beda = -1-(-5) = 5-1 = 4
-> Beda (b) = 4
Suku ke-18 berarti
-> n = 18
Ditanya suku ke-18
Un = a+b(n-1)
U₁₈ = -5+4(18-1)
U₁₈ = -5+72-4
U₁₈ = 63
Suku ke-18 = 63
------------------------
[d] {-6, -3, 0, 3}
-> Suku pertama (a) = -6
beda = -3-(-6) = 6-3 = 3
-> Beda (b) = 3
Suku ke-25 berarti
-> n = 25
Ditanya suku ke-25
Un = a+b(n-1)
U₂₅ = -6+3(25-1)
U₂₅ = -6+75-3
U₂₅ = 75-9
U₂₅ = 66
Suku ke-25 = 66
------------------------
[e] {5, 3¾, 2½, 1¼}
-> Suku pertama (a) = 5
beda = 3¾-5 = -(5-3¾) =
-(5-(3+¾)) = -(5-3-¾) =
-(2-¾) = -(2-1 + 1-¾) =
-(1 + ⁴/₄-¾) = -(1+¼)
-> Beda (b) = -1 ¼
Suku ke-20 berarti
-> n = 20
Ditanya suku ke-20
Un = a+b(n-1)
U₂₀ = 5+(-1 ¼)(20-1)
U₂₀ = 5+(-(1+¼))(19)
U₂₀ = 5+(-1-¼)(19)
U₂₀ = 5-19-¹⁹/₄
U₂₀ = -(19+¹⁹/₄-5)
U₂₀ = -(14+¹⁹/₄)
U₂₀ = -(14+⁽¹⁶⁺³⁾/₄)
U₂₀ = -(14+¹⁶/₄+¾)
U₂₀ = -(14+4+¾)
U₂₀ = -(18+¾)
U₂₀ = -18 ¾
Suku ke-20 = -18 ¾
-----------------------------
(xcvi)