# 中學英數學題

Help! Please to slove the above questions~

### 2 個解答

• ?
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

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