PromotionBanner

解答

1. Un = a - (n-1).b

U50 = 27 - (50-1.)4

= 27 - 196

= -169

2. a = -1

b=3-(-1) = 4

Sn = n/2 (2a + (n-1)b)

S50=50/2 ( 2(-1) + (50-1)4)

S50 = 25 (-2+ 196 )

S50 = 25 (194)

S50 = 4850

Maret's

makasih banyak

留言
您的問題解決了嗎?