dik u3=11 u7=27 dit=u12......?tolong di jawab ya teman-teman

Bab : Barisan dan Deret
Kelas : IX SMP

U3 = U1 + 2b = 11
U7 = U1 + 6b = 27
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=======> -4b = -16
=======> b = 4

U3 = U1 + 2b
11 = U1 + 2(4)
11 = U1 + 8
U1 = 11 - 8
U1 = 3

U12 = U1 + 11b
U12 = 3 + 11(4)
U12 = 3 + 44
U12 = 47