[問題] GWD7-Q28

[kwtluck]

Q28:
A straight line in the xy-plane has a slope of 2 and a y-intercept of 2. On this line, what is the x-coordinate of the point whose y-coordinate is 500 ?

A.249
B.498
C.676
D.823
E.1,002

Answer: A =>麻煩各為大大解題i76 Thanks!!~~

[QQA]

參考前人解法如下:

http://www.formosamba.com/phpBB3/viewtopi ... -intercept

[kwtluck]

**感謝QQA大大**
[前人做法]
斜率為 2 代表y/x=2 加上截距為2
所以公式應該是 y=2x+2
所以當 y=500 時 x=(500-2)/2=249

直線方程式: by=ax+c 其斜率不是-b/a
想順待釐清觀念
兩線垂直斜率相乘= -1
兩線平行斜率相等
兩點求一直線= (x-x1)/(y-y1)= (x-x2)/(y-y2)
請問各位大大這樣對嗎?
Thanks!!~~