Suku ke 28 dari barisan 15, 24,35 48,63,

A = 15
B = 24 – 15 = 9
n = 28
Un = A + B ( n – 1 )
U28 = 15 + 9 ( 28 – 1 )
U28 = 15 + 9 ( 27 )
U28 = 15 + 243
U28 = 258

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