在矩形ABCD中,AB=8,AD=6,动点P从A出发,以每秒一个单位的速度沿着A,B,C,D的顺序运动.到D的时候停止.
10个回答

1.

(a) t ≤8, P在AB上

S = (1/2)*AP*AD = (1/2)*t*6 = 3t

(b) 8 < t ≤ 14, P在BC上

S = (1/2)*AD*AD上的高= (1/2)*6*8 = 24

(c) 14 < t ≤ 22, P在CD上

DP = 22-t

S = (1/2)*DP*AD = (1/2)(22-t)*6 = 3(22 - t)

2.

S = 3t = 15, t = 5

或S=3(22-t) = 15, t =17

3. 有三种可能:

(a)P在AB上, PA =AD = 6

t = 6

(b) P在BC上, 显然P为BC的中点, BP = 3

t = 8 + 3 = 11

(c) P在CD上, AD = DP = 6

t = 8 +6 + (8-6) = 16