tentukan u45 (pada barisan aritmetika) jika diketahui = a. u11=400 & u51=520 b. u2=200 & u32=140

Un = a + ( n - 1 ) b

a) U11 = a + 10b = 400
U51 = a + 50b = 520
--------------------------------(-)
- 40b = - 120
b = 3
a + 10b = 400
a + 10(3) = 400
a + 30 = 400
a = 400 - 30
a = 370
U45 = a + 44b
= 370 + 44(3)
= 370 + 132
= 502

b) U2 = a + b = 200
U32 = a + 31b = 140
------------------------------(-)
- 30b = 60
b = - 2
a + b = 200
a - 2 = 200
a = 200 + 2
a = 202
U45 = a + 44b
= 202 + 44(-2)
= 202 - 88
= 114