數學練習[中4][10分]

1. y = a(x-1)(x+3)
sub pt. P (2,5 )into the equation
5 = a (2-1)(2+3)
a = 1

2. by (1) a =1 , y = (x-1)(x+3) = x^2 + 2x -3
x^2 + 2x -3 = 0
(x+3)(x-1) = 0
x = -3 or 1
so, A (-3,0) , B (1,0)

when x=0 , y =(x-1)(x+3) = (0-1)(0+3) = -3
so ,C (0,-3)

3. by (1) ,(2) , y = x^2 + 2x -3
y= (x+1)^2 -4
vertex coordinate : (-1 ,-4)

4. by (1),(2),(3) , AB = 4 units , OC = 3 units
the are of thee triangle ABC :
(AB x OC)/2 = 4 x 3 / 2 = 6 sq units

2008-09-27 12:03:18 補充：
sorry 4 . should be :
4. by (1),(2),(3) , AB = 4 units , OC = 3 units
the area of thee triangle ABC :
(AB x OC)/2 = 4 x 3 / 2 = 6 sq. units

2008-09-27 12:03:54 補充：
the area of thee triangle ABC : -->
the area of the triangle ABC