Diket.barisan aritmatika suku ke.9=35 Dan U4+U12=62. Tent. Rumus Un

62 = (35-5b) + (35+3b)
62 = 70 - 2b
2b = 8
b = 4
maka, U1 = 35 - 8b = 35 - 32 = 3

Un = 3 + (n-1)4

U9= 35
U4+U12=62.
a+8b =35
a+3b + a+11b =62
a+8b=35          x2
2a+14b=62      x1

substitusikan
2a+16b =70
2a+14b=62 sama sama di kurang

2b= 8
b= 4

2a +16(4)=70
2a=70-64
a=3

Un=a+(n-1)b
=3+(n-1)4
=3+4n-4
=-1+4n