Tentukan fungsi kuadrat yang grafiknya (-1,1), (0,4), (1,-5) Tolong penjelasan tentang cara mendapatkan nilai A nya kakak

<p>Jawaban yang tepat adalah <strong>y = -6x² - 3x + 4</strong></p><p>&nbsp;</p><p>Pembahasan :</p><p>Rumus Umum :</p><p>y = ax² + bx + c</p><p>&nbsp;</p><p><strong>Melalui (-1,1)</strong></p><p>y = ax² + bx + c</p><p>1 = a(-1)² + b(-1) + c</p><p>1 = a - b + c &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</p><p>b = a + c - 1 &nbsp; &nbsp; (1)</p><p>&nbsp;</p><p><strong>Melalui (0,4)</strong></p><p>y = ax² + bx + c</p><p>4 = a(0)² + b(0) + c</p><p>c = 4 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(2)</p><p>&nbsp;</p><p><strong>Melalui (1,-5)</strong></p><p>y = ax² + bx + c</p><p>-5 = a(1)² + b(1) + c</p><p>-5 = a + b + c &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(3)</p><p>&nbsp;</p><p>Substitusikan c = 4 ke persamaan (1)</p><p>b = a + c - 1</p><p>b = a + 4 - 1</p><p>b = a + 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(4)</p><p>&nbsp;</p><p>Substitusikan persamaan (4) &nbsp;dan c = 4 ke persamaan (3)</p><p>-5 = a + b + c &nbsp;</p><p>-5 = a + a + 3 + 4</p><p>-5 = 2a + 7</p><p>2a = -5 - 7</p><p>2a = -12</p><p>a = -12/2</p><p>a = -6</p><p>&nbsp;</p><p>Substitusikan a = -6 ke persamaan (4)</p><p>b = a + 3&nbsp;</p><p>b = -6 + 3</p><p>b = -3</p><p>&nbsp;</p><p>Substitusikan a = -6, b = -3 dan c = 4 ke rumus umum</p><p>y = ax² + bx + c</p><p><strong>y = -6x² - 3x + 4</strong></p><p>Jadi rumus fungsi kuadratnya adalah <strong>y = -6x² - 3x + 4</strong></p>