plis tolong lg ulangan

Dik : a = 16 b = 5
Dit : u30? S30?
Jawab :
U30 = a + b × (n-1)
U30 = 16 + 5 × (30-1)
U30 = 16 + 5× (29)
U30 = 16 + 145
U30 = 165 kursi

S30 = n/2 × (2a + b× (n-1))
S30 = 30/2 × ( 2(16) + 5×(30-1))
S30 = 15 × (32 + 145)
S30 = 15 × 177
S30 = 2655 kursi