Jawablah pertanyaan berikut

<p>Jawaban yang tepat adalah C. Memotong sumbu x di x = 1 dan x = -7</p><p>&nbsp;</p><p>Pembahasan :</p><p>f(x) = (x + 1)(x - 7)</p><p>f(x) = x² - 7x + x &nbsp;- 7</p><p>f(x) = x² - 6x - 7</p><p>a = 1, b = -6 dan c = -7</p><ul><li>a &gt; 0, <strong>maka grafik membuka ke atas&nbsp;</strong></li><li>Sumbu simetri, x = -b/2a = -(-6)/2(1) = 6/2 = <strong>3</strong></li><li>Nilai minimum, y = (b² - 4ac)/-4a</li></ul><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= ((-6)² - 4(1)(-7))/-4(1)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= (36 + 28)/-4</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 64/-4</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= <strong>-16</strong></p><ul><li>Memotong sumbu x, y = 0</li></ul><p>&nbsp; &nbsp; &nbsp; x² - 6x - 7 = 0</p><p>&nbsp; &nbsp; &nbsp;((x + 1)(x - 7) = 0</p><p>&nbsp; &nbsp; &nbsp;<strong>x = -1 atau x = 7</strong></p>