抛物线过A(-1,0),B(3,0), 则抛物线可表达为y = a(x+1)(x-3) = ax² -2ax -3a
抛物线过C(0,-1), -3a = -1, a = 1/3
y = (x+1)(x-3)/3
AB长为4,所以PQ的长也是4.因Q在y轴上,满足该条件的P点的横坐标必然为4或-4.
1. P点的横坐标为4,P(4, 5/3)
2. P点的横坐标为-4,P(-4, 7)
抛物线过A(-1,0),B(3,0), 则抛物线可表达为y = a(x+1)(x-3) = ax² -2ax -3a
抛物线过C(0,-1), -3a = -1, a = 1/3
y = (x+1)(x-3)/3
AB长为4,所以PQ的长也是4.因Q在y轴上,满足该条件的P点的横坐标必然为4或-4.
1. P点的横坐标为4,P(4, 5/3)
2. P点的横坐标为-4,P(-4, 7)