A.Maths Straight Lines
2008-06-14 7:25 pm
A straight line L passes through the point (1,3) .If the area of the triangle enclosed by the line L and the positive axes is 6.25 sq.units, find the equations of L.
回答 (2)
2008-06-14 7:51 pm
✔ 最佳答案
Let the equation of the line be y-3=m(x-1)i.e. mx-y-m+3=0
x=0, y=3-m
y=0, x=(m-3)/m
∴(3-m)[(m-3)/m]/2=6.25
m²-6m+9+12.5m=0
2m²+13m+18=0
(2m+9)(m+2)=0
m=-9/2 or -2
When m=-9/2, equation of L is 9x+2y-15=0
When m=-2, equation of L is 2x+y-5=0
2008-06-14 9:16 pm
method 1:
pt slope form: x/a +y/b =1
代 (1,3)落去
1/a + 3/b =1
ab/2 =6.25
solve 以上兩式
pt slope form: x/a +y/b =1
代 (1,3)落去
1/a + 3/b =1
ab/2 =6.25
solve 以上兩式
參考: Chung Tai Additional Pure Mathematics
收錄日期: 2021-04-23 23:00:07
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080614000051KK00675