diketahui barisan aritmatika 3, 7, 11, 15 . . . . tentukan U15 dan U30

U15 = a + (n-1) b
= 3 + (15-1) 4
= 3 + 14 × 4
= 3 + 56
= 59

U30 = a + (n-1) b
= 3 + (30-1) 4
= 3 + 29 × 4
= 3 + 116
= 119

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