10正确,不再重复.
a = 2, b = √21, c = √(4 + 21) = 5
假定取右焦点F2(5, 0), 左顶点为A1(-2, 0), 距离=7 > 6, 即该点只能在双曲线右支上
如消去的纵坐标,可得: (5x - 16)(5x + 8) = 0
x = 16/5 (答案是10)
x = -8/5 (在双曲线左支上, 舍去)
取左焦点结果一样.
10正确,不再重复.
a = 2, b = √21, c = √(4 + 21) = 5
假定取右焦点F2(5, 0), 左顶点为A1(-2, 0), 距离=7 > 6, 即该点只能在双曲线右支上
如消去的纵坐标,可得: (5x - 16)(5x + 8) = 0
x = 16/5 (答案是10)
x = -8/5 (在双曲线左支上, 舍去)
取左焦点结果一样.