a) let the coordinates of B are (0 , b) and the coordinates of A are (a ,0)
when x = 0 y= b
b=4
when x = a y=0
a= -2
b) the slope of L2 = (-1) /2
= - 1/2
the equation of L2 is
-1/2 = y-4 / x-0
-x-2y+8=0
x+2y-8 =0
c) 唔想做
32 自己做啦作者: ~不問世事~ 時間: 11-9-22 09:28 PM
31a)A(-2,0) B(0,4)
31b)x+2y+c=0---(*)
sub. B(0,4) into (*),c=-8
past paper 黎-.-?
睇marking / solution 幫到你作者: 凸唯而出 時間: 11-9-22 10:36 PM
本帖最後由 凸唯而出 於 11-9-22 10:36 PM 編輯
31
y = mx + c
we have
2x - y +4 =0
thus that y = 2x + 4
Since B is on the y-axis, let it be (0,y)
y = 2(0) +4
y = 4
Since A is on the y-axis, let it be (x,0)
0 = 2x + 4
x = -2
A = (-2,0) , B = (0,4)
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slope of L1 is 2
slope of L1 x slope of L2 = -1 ( perpendicular)
2 x slope of L2 = -1
slope of Lx = - 1/2
let anther point on L2 be ( x , y)
y - 4 1
-------- = - ---
x - 0 2
2y -8 = - x
2y + x -8 =0
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計左 a 同 b , 之後你識的
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32
let another point on the line be (x,y)
y - 3 - 4
------ = ---
x - 10 3
3y + 4X - 49 = 0
----------------------------
3-h -4
----- = ---
10- 3 3
h = 15
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i 同 b 一樣禁計
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ii 之後你識計的