Jawapan

2016-01-25T01:35:06+08:00
The number 15 have to  substitute into the equation. so, 5(15)-6=69
 

2016-01-25T02:16:18+08:00
Un = 5n - 6

U1 = 5(1) - 6
= 5 - 6
= -1

U2 = 5(2) - 6
= 10 - 6
= 4

beza sepunya, d
= 4 - (-1)
= 5

S15
= 15/2 [2(-1) + 14(5)]
= 15/2 [-2 + 70]
= 15/2 [68]
= 510