茅责咚
幼苗
共回答了25个问题采纳率：88% 举报
x²+y²-2ax+4y+a²-5=0
(x - a)² + (y + 2)² = 9,圆心A(a,-2),半径R = 3
x²+y²-2x-2ay+a²-3=0
(x -1)² + (y -a)² = 4,圆心B(1,a),半径r = 2
二者外切,AB = R+r = 5
AB² = 25 = (a - 1)² + (-2 - a)² = 2a² + 6a + 5
a² + 3a - 10 = 0
(a + 5)(a - 2) = 0
a = -5或a = 2
1年前
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