Alfiyah N

27 November 2023 12:30

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Alfiyah N

27 November 2023 12:30

Pertanyaan

Jawablah pertanyaan berikut

Jawablah pertanyaan berikut 

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Jawaban terverifikasi

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Sumber W

Community

12 Desember 2023 01:08

Jawaban terverifikasi

<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) = x<sup>2</sup> - 7x + x &nbsp;- 7</p><p>f(x) = x<sup>2</sup> - 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 = (b<sup>2</sup> - 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)<sup>2</sup> - 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; x<sup>2</sup> - 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>

Jawaban yang tepat adalah C. Memotong sumbu x di x = 1 dan x = -7

 

Pembahasan :

f(x) = (x + 1)(x - 7)

f(x) = x2 - 7x + x  - 7

f(x) = x2 - 6x - 7

a = 1, b = -6 dan c = -7

  • a > 0, maka grafik membuka ke atas 
  • Sumbu simetri, x = -b/2a = -(-6)/2(1) = 6/2 = 3
  • Nilai minimum, y = (b2 - 4ac)/-4a

                                           = ((-6)2 - 4(1)(-7))/-4(1)

                                           = (36 + 28)/-4

                                           = 64/-4

                                           = -16

  • Memotong sumbu x, y = 0

      x2 - 6x - 7 = 0

     ((x + 1)(x - 7) = 0

     x = -1 atau x = 7


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