Jawab pakai cara ya :)​

4. 1, 3, 6, 10, 15

pola Un = 1/2 x n x (n + 2)

5. Un = 4n

Penjelasan dengan langkah-langkah:

4. bilangan segitiga memiliki pola

Un = 1/2 n (n + 1)

U1 = 1/2 x 1 x (1 + 1) = 1/2 x 2 = 1

U2 = 1/2 x 2 x (2+1) = 1 x 3 = 3

U3 = 1/2 x 3 x (3+1) = 1/2 x 3 x 4 = 6

U4 = 1/2 x 4 x (4+1) = 3 x 5 =10

U5 = 1/2 x 5 x (5+1) = 1/2 x 5 x 6 = 15

5. U1 = 4

b = 8 – 4 = 4

Un = U1 + (n – 1)b

= 4 + (n – 1)4

= 4 + 4n – 4

= 4n