过定点(1,2),可作两条直线与圆x²+y²+2kx+2y=k²+1相切,则实数k的取值范围?
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![过定点(1,2),可作两条直线与圆x²+y²+2kx+2y=k²+1相切,则实数k的取值范围?](/uploads/image/z/12052188-36-8.jpg?t=%E8%BF%87%E5%AE%9A%E7%82%B9%EF%BC%881%2C2%29%2C%E5%8F%AF%E4%BD%9C%E4%B8%A4%E6%9D%A1%E7%9B%B4%E7%BA%BF%E4%B8%8E%E5%9C%86x%26%23178%3B%2By%26%23178%3B%2B2kx%2B2y%3Dk%26%23178%3B%2B1%E7%9B%B8%E5%88%87%2C%E5%88%99%E5%AE%9E%E6%95%B0k%E7%9A%84%E5%8F%96%E5%80%BC%E8%8C%83%E5%9B%B4%3F)
过定点(1,2),可作两条直线与圆x²+y²+2kx+2y=k²+1相切,则实数k的取值范围?
过定点(1,2),可作两条直线与圆x²+y²+2kx+2y=k²+1相切,则实数k的取值范围?
过定点(1,2),可作两条直线与圆x²+y²+2kx+2y=k²+1相切,则实数k的取值范围?
x²+y²+2kx+2y=k²+1
即(x+k)²+(y+1)²=2k²
要满足条件,
则(1,2)在圆外,
∴ (1+k)²+(2+1)²>2k²
即 k²-2k-10