U1=5 b=3 U5=....? S10=....?

Materi : Barisan dan deret
Kelas : IX SMP

Un = U1 + (n - 1)b
U5 = 5 + (5 - 1) 3
U5 = 5 + 4 . 3
U5 = 5 + 12
U5 = 17

Sn = n/2 ( 2.U1 + (n - 1)b)
S10 =10/2 ( 2 . 5 + (10 - 1) 3)
S10 = 5 ( 10 + 9 . 3 }
S10 = 5 ( 10 + 27 )
S10 = 5 ( 37 )
S10 = 185

U5 = a + (n-1)b = a + 4b = 5 + 4(3) = 5 + 12 = 17

S10 = n/2 (a + a + (n-1)b) = 10/2 (5 + 5 + 9(3)) = 5 (10 + 27) = 5(37) = 185