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4 years ago

5

X+y+z =4

1 answer:

cestrela7 [59]4 years ago

4 0

<span><span> <span>Akar akar persamaan kuadrat 2x² - 3x -1 = 0 adalah x1 dan x2. Persamaan kuadrat baru yang akar akarnya satu lebih kecil dari dua kali akar akar persamaan kuadrat di atas adalah ........</span></span><span><span><span>A.x² - x - 4 = 0</span><span>B.x² + 5x - 4 = 0</span><span>C.x² - x + 4 = 0</span></span><span><span>D.x² + x + 4 = 0</span><span>E.x² - 5x - 4 = 0</span></span></span><span>Jawaban : A
Penyelesaian :
Akar-akar persamaan lama :  x1 dan x2

Akar-akar persamaan baru :  xA dan xB
                                             xA = 2x1 - 1
                                             xB = 2x2 - 1
                                             xA + xB  = (2x1 - 1) + (2x2 - 1)
                                                           = 2 (x1 + x2) - 2
                                                           = 2 () - 2
                                                           = 3 - 2
                                              xA + xB = 1

                                              xA . xB = (2x1 - 1) (2x2 - 1)
                                                          = 4 x1.x2 - 2(x1 + x2) + 1
                                                          = 4.(-) - 2() + 1
                                                          = -2 - 3 + 1
                                              xA . xB = -4

Jadi persamaan kuadrat baru : x² - (xA + xB)x + xA . xB = 0
                                              x² - x - 4 = 0

</span></span>

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