Diketahaui: U3=14 U40=125 U25=?? Carilah U25 tolong dijawab dgn cara.. plissss

Un = a + (n-1) b

U3 = a + (3-1) b
14 = a + 2b

U40 = a + (40-1) b
125 = a + 39b

Di eliminasi
14 = a + 2b
125 = a + 39b
___________ -
-111 = -37b
b = - 111 ÷ -37
b = 3

Mencari nilai a
14 = a + 2b
14 = a + 2(3)
14 = a + (6)
14 = a + 6
a = 14 - 6
a = 8

U25 = a + (25-1) b
= 20 + 24 (3)
= 20 + 72
= 92