jumlah n suku pertama suatu deret adalah S n = 3n 2 - 5n suku ke sepuluh deret tersebut adalah...

<p>Jawaban yang tepat adalah U₁₀ = 52</p><p>&nbsp;</p><p>Pembahasan :</p><p>S_n = 3n² - 5n</p><ul><li>S₁ = 3(1)² - 5(1)</li></ul><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 3 - 5</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = -2</p><p>&nbsp; &nbsp; &nbsp; &nbsp; S₁ = U₁ = a = -2</p><ul><li>S₂ = 3(2)² - 5(2)</li></ul><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 3(4) - 10</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 12 - 10</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 2</p><ul><li>S₃ = 3(3)² - 5(3)</li></ul><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 3(9) - 15</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 27 - 15</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 12</p><p><strong>Menentukan Suku ke-2 dan suku ke-3</strong></p><ul><li>U₂ = S₂ - S₁</li></ul><p>_{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}= 2 - (-2)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 2 + 2</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 4</p><ul><li>U₃ = S₃ - S₂</li></ul><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 12 - 2</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 10</p><p><strong>Menentukan beda</strong> <strong>(b)</strong></p><p>b = U₂ - U₁</p><p>&nbsp; &nbsp; = 4 - (-2)</p><p>&nbsp; &nbsp; = 4 + 2</p><p>&nbsp; &nbsp; = 6</p><p><strong>Menentukan Suku ke-10 (U₁₀)</strong></p><p>U_n = a + (n - 1)b</p><p>U₁₀ = -2 + (10 - 1)6</p><p>&nbsp; &nbsp; &nbsp; &nbsp; = -2 + (9).6</p><p>&nbsp; &nbsp; &nbsp; &nbsp; = -2 + 54</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 52</p><p>Jadi suku ke-10 adalah 52&nbsp;</p>