a=16, n=30, dan b=-2,carilah u30 dan s30

Dik. Barisan deret aritmatika :
a = 16, n = 30, b = -2.
Dit. U30 & S30 ?

Jawab...

u30 = a +29b
u30 = 16 + 29 (-2)
u30 = 16 -58
u30 = -42

Sn = n/2 (2a + (n -1) b)
S30 = 30/2 (2(16) + (29) (-2))
S30 = 15 ( 32 - 58)
S30 = 15 ( -26)
S30 = -390

Semoga membantu... ^_^