MATHS.. 20分

slope of L1=5 and the y-intercept of L1=10
Since L is perpendicular to L1 a, so the slope of L =-1/5
(since slope of L1 * slope of L=-1)
so L:y=-1/5x+C where C is a real constant

Since L1 and Lhave the same y-intercept
So, sub (0,10)in to L

10=C

So y=-1/5X+10

5Y=-X+10
x+5y-50=0

2007-11-11 08:10:35 補充：
根據我中七讀數ge學識 我a maths拎b

y-intercept of L1:(同L的y-intercept一樣)
5x-y+10=0
y = 10((put x=0)

slope of L1:
- [ (5) / (-1) ]
=5

因為L perpendicular to L2
所以 slope of L x slope of L2 = -1
slope of L x 5 = -1
slope of L = -1/5

所以有y-intercept:10, 即係有點: ( 0,10 )
同埋 slope: -1/5
就可以搵到equation of L

equation of L:
(y-10) / (x-0) = -1/5
5(y-10) = -x
x + 5y - 50 = 0

其實識做一題未代表識做第2條
有幾條主要公式一定要識左先可以識做晒
加油:)"
有問題歡迎sd email問我

step 1:find the same y intercept L &L1,
let x=0,sub into L1,
so, y=10
thus, their interception point at (0,10)

step 2: find grandient of L1,
grandient of L1= -5/-1
=5

step3:find grandient of L,
grandient of L = -1/5

step4:equation of L,
y-10= -1/5(x-0)
5y-50= -x
x+5y-50=0

hope u can understand...thx!!