中學英數學題

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2 個解答

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  • ?
    Lv 5
    9 年前
    最愛解答

    15.

    A (-2,-4) , B (4,5) and AP : PB = 2 : 1

    x-coord of P: [2(4) + 1(-2)] / (2+1) = 2

    y-coord of P: [2(5) + 1(-4)] / (2+1) = 2

    16. (can't see the values)

    17a.

    A (2a,2a) , B (6a,-a)

    AB = sqrt[(2a-6a)^2 + (2a+a)^2] = sqrt(25a^2) = 5a

    17b.

    C (0,7) , D (-3,3)

    CD = sqrt[(0+3)^2 + (7-3)^2] = sqrt(25) = 5

    AB = 3CD => 5a = 3(5) => a = 3

    18a.

    P (2,-1) , Q (-1,2) , R (1,-2) , S (a,b)

    slope PQ: (-1-2)/(2+1) = -1

    slope RS: (-2-b)/(1-a)

    (-2-b)/(1-a) = -1

    -2-b = -(1-a)

    -2-b = -1+a

    a+b = -1

    18b.

    T (-3,c)

    equation of RS: y+2 = -1(x-1) => x + y = -1

    when x = -3, y = c = 2

    19a.

    A (6,2) , B (8,1)

    slope AB: (2-1)/(6-8) = -1/2

    19b.

    equation of AB: (y-2) = (-1/2)(x-6)

    2(y-2) = -x + 6

    x + 2y = 10

    when y = 0, x = 10

    19c.

    slope AD: -1/slope AB = -1/(-1/2) = 2

    equation of AD: y-2 = 2(x-6)

    when y = 0, x = 5

    20. (can't see the values)

    21a.

    A (-7,9) , B (-2,-1) , P (p,3)

    slope AB: (9+1)/(-7+2) = -2

    equation of AB: y+1 = (-2)(x+2)

    2x + y = -5

    when y = 3, x = -4, thus P (-4,3)

    AP = sqrt[(-7+4)^2 + (9-3)^2] = sqrt(45)

    PB = sqrt[(-4+2)^2 + (3+1)^2] = sqrt(20)

    AP : PB = sqrt(45) : sqrt (20) = 2 : 3

    21b.

    p = -4 (above)

  • 9 年前

    字细,睇唔到-------

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