[問題]GWD6 Q9

[val]

In the x-y plane, the point (-2, -3) is the center of a circle. The point (-2, 1) lies inside the circle and the point (4,-3) lies outside the circle. If the radius r of the circle is an integer, then r=

A. 6
B. 5
C. 4
D. 3
E. 2

The ans. is (B) 5. Why? Can someone please explain the solution?

Thanks!

[enim]

圓心為(-2，-3)
一點(-2，1)在圓內
一點(4，-3)在圓外
他說半徑是整數
所以你就算出圓心跟圓內那一點的距離...為4
圓心跟圓外那一點的距離...為6
所以r=5

[val]

阿 原來我看錯題目了 謝謝你 另我恍然大悟我的粗心