✔ 最佳答案
a.) Let 1:x be the ratio of BD:DC.
{section formula, 因為知道D既x-coordinate 係0, 所以攞B同C既x-coordinate就計到答案}
[(6)(x)+(-3)(1)]/(1+x)=0
6x-3=0 or x=0(rej.)
x=1/2
Hence, the ratio of BD:DC is 2:1
b.) Let y be the y-intersect of BC.
[(4)(1)+(7)(2)]/(1+2)=y
y=6
c.)Slope of BC: (7-4)/(-3-6)=-1/3
Slope of AD: (6-k)/(0+2)=(6-k)/2
Since AD丄BC, Slope of BC*Slope of AD=-1
-1/3*(6-k)/2=-1
1/3*(6-k)/2=1
6-k=6
-k=0
k=0
d.)我唔知你有冇讀AMaths, 因為AMaths 有個方法比較快
非AMaths 方法:
Distance of BC: √[(-3-6)²-(7-4)²]=√90
Distance of AD: √[(0-6)²-(-2-0)²]=√40
Area of △ABC =√90*√40/2=√3600/2=60/2=30 sq. units
AMaths 方法:
Area of △ABC:
| 6 4 |
| -2 0 |
1/2 * | |
| -3 7 |
| 6 4 |
= 1/2* [(-8+0+42)-(0-14-12)]
= 30 sq. units
希望幫到你