U1=k-1,U3=3k+1,U10=98.U6=...

Mapel : Matematika
Kelas : IX SMP
Bab : Barisan dan deret

Pembahasan :
2(U2) = U1 + U3
2(U2) = (k - 1) + (3k + 1)
2U2 = 4k
U2 = 2k

Beda = U2 - U1
Beda = 2k - (k - 1)
Beda = 3k + 1

U10 = 98
a + 9b = 98
k - 1 + 9(3k + 1) = 98
k - 1 + 27k + 9 = 98
28k + 8 = 98
28k = 90
k = 90/28
k = 45/14

Beda = 3k + 1
Beda = 3(45/14) + 1
Beda = 149/14

a = k - 1
a = 45/14 - 1
a = 31/14

U6 = a + 5b
U6 = 31/14 + 5(149/14)
U6 = 31/14 + 745/14
U6 = 766/14
U6 = 383/7

dik:
U1=k-1
U3=3k+1
U10=98

U2=U1-b
=k-1-b
b=?

dit:
U6=?

jwb:
U3-U2
=U2-U1
=3k+1-(k-1+b)
=(k-1+b)-(k-1)
=3k-k+1+1
=2b 2k+2=2b

b=k+1 U10
=a+9b 98
=(k-1)+9(k+1) 98
=k-1+9k+9 98
=10k+8 98-8
=10K 90
=10k 90/10
=k
k=9 U1
=a=k-1=9-1=8
b=k+1=9+1=10
U6=a+5b
U6=8+5×10
U6=8+50
U6=58