(5分)中三數1題,關於distance formula

Given that the distance between M(m,9) and N(2,-1) is 5√5 units, find all the possible values of m.
√[(m-2)^2 + (9+1)^2]=5√5
[(m-2)^2 +10^2]=(5√5)=125
(m-2)^2=125-100
(m-2)^2=25
m-2 = 5 or -5
m=7 or -3
如有不足/有錯
請發信聯絡
另外，嚴禁抄襲！
加我好友^_^

2008-11-13 17:43:57 補充：
下面那個做咩用f5 circle?? (or f4 A math)
人地就咁用distance formula
你let乜鬼circle= =

Let x, y be centre,
Let x1, y1 be a point in circle.
(x - x1)^2 (y - y1)^2 = r^2
N is centre and M is a point in circle
therefore, (2-m)^2 (-1-9)^2 = (5√5)^2
4-4m m^2 100=125
m^2-4m-21=0
(m-7)(m 3)=0

m=7 or -3