barisan aritmatika u2= -10 dan u7=45 maka u15 adalah

jadi, U15 = 133
a = -21
b = 11

U2 = a + b
-10 = a + b
a = -10-b

U7 = a + 6b
45 = a +6b
Disubtitusi nilai a nya
45 = -10-b + 6b
55 = 5b
b = 11
a = -10-11
= -21

U15 = a + 14b
= -21 + 14(11)
= 133