Matematika

Pertanyaan

tentukan persamaan garis singgung parabola (y+3)²= 4(x-2) yang sejajar garis 2x+y-5=0

2 Jawaban

  • jawab

    m garis  2x + y - 5= 0
    m = - 2

    y' = 0
    2(y+3)y' = 4
    y' = 4/(2y+ 6)
    y' = -2

    4/(2y + 6) = - 2
    4 = - 2(2y + 6)
    4 = - 4y -12
    4y = -16
    y = - 4  subke (y+3)² = 4(x - 2)
    (-4+3)²= 4( x- 2)
    1 = 4x - 8
    4x = 9
    x = 9/4

    y - y1 = m(x - x1)
    y - (-4) = -2(x  -9/4)
    y + 4 = -2x + 9/2
    2y + 8 = - 4x + 9
    4x + 2y - 1= 0

  • Misal :
    Pers garis singgung :
    y = mx + c

    2x + y - 5 = 0
    m1 = -a/b = -2

    sejajar : m = m1 = -2

    y = -2x + c
    substitusi kab ke (y + 3)² =4(x - 2)

    (-2x + c)² = 4x - 2
    4x² - 4cx -4x + c² + 2 = 0
    4x² - (4 + 4c)x + (c² + 2) = 0
    2x² - (2 + 2c)x + (c² + 2)/2 = 0

    Menyinggung : D = 0

    D = 0
    b² - 4ac = 0
    (2 + 2c)² - 4.2.(c² + 2)/2 = 0
    (2 + 2c)² - 4c² - 8 = 0
    8c - 4 = 0
    c = 1/2

    Persamaan garis singgung
    y = mx + c
    y = -2x + 1/2
    2y = -4x + 1
    4x + 2y - 1 = 0

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