amath

2007-12-20 6:07 am

find the range of value F such that x^2+y^2-4x-6y+F=0 is a real circle

回答 (1)

2007-12-20 9:34 pm

✔ 最佳答案

For real circle, radius>0
radius=(-4/2)^2+(-6/2)^2-F>0
∴13-F>0
F<13

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