Question

Jumlah dari barisan: 1+3+5+...+15 adalah...
help me please

Answer 1

A = 1
b = 3 - 1 = 2
Un = 15
Un = a + (n - 1)b
15 = 1 + 2n - 2
2n = 16
n = 8
S8 = 4(2(1) + 7(2))
     = 4(2 + 14)
     = 4(16)
     = 64

Answer 2

A=I
b=3-I=2
Un=a+(n-I)b
Un=I+(n-I)2=I5
= I+2n-2=I5
2n =I6
n. = 8
Sn=I/2n (2a+(n-I)b)
S8=I/2.8(2.I+(7)2)
=4 (2+I4)
= 4(I6)
= 64