[問題]天山9-34

[usamiyo]

If Line K in the xy-plane has equation y=mx+b, where m and b are constants, what is th eslope of K?

1. K is parlled to the line with equation y=(1-m)x+b+1
2. K intersects teh line with equation y=2x+3 at the point (2,7)

Ans: A

我選B耶! 為何是A不是B呢?

[StanleyHuang]

y=mx+b，斜率就是 m，題目問說 m = ??
1) K 平行 y=(1-m)x+b+1 ==> m = (1-m) ==> m = 1/2
2) (2,7)代入 y=mx+b 只得到 7=2m+b ==> 沒有b 算不出 m
所以選 (A)