中四數學高手請入

x^2 + y^2 = c^2
x^2 + 2xy + y^2 -2xy = c^2
(x + y)^2 -2xy = c^2
c^2 - 2xy = c^2 since x + y = c
2xy = 0
So, x = 0 or y = 0
When x = 0, y^2 = c^2
y = +/- c;
When y = 0, x^2 = c^2
x = +/- c

2008-06-05 16:38:29 補充：
x^2 + y^2 = c^2
x^2 + 2xy + y^2 -2xy = c^2
(x + y)^2 -2xy = c^2
c^2 - 2xy = c^2 since x + y = c
2xy = 0
So, x = 0 or y = 0
When x = 0, y^2 = c^2
y = +/- c;
When y = 0, x^2 = c^2
x = +/- c

2008-06-05 16:38:36 補充：
x^2 + y^2 = c^2
x^2 + 2xy + y^2 -2xy = c^2
(x + y)^2 -2xy = c^2
c^2 - 2xy = c^2 since x + y = c
2xy = 0
So, x = 0 or y = 0
When x = 0, y^2 = c^2
y = +/- c;
When y = 0, x^2 = c^2
x = +/- c

x^2 + y^2 = c^2 -------------(1)
x +y = c ----------------------(2)

代 (2) 入 (1) ,
x^2 + y^2 = (x+y)^2
x^2 + y^2 = x^2 + 2xy + y^2
0 = 2xy
x = 0 OR y = 0

代 x = 0 入 (1) ,
y = c

代 y = 0 入 (1) ,
x = 0

所以 , 當 x=0 , y=c ; 當y=0 , x=c

首先, 你俾嘅答案已經好有問題:
y=c ,x=c
既然x + y = c, 咁如果x=y=c, 加埋就係x+y=2c,
除非c=0, 如果唔係個答案就唔成立啦

x^2 + y^2 = c^2
x^2 + 2xy + y^2 -2xy = c^2
(x + y)^2 -2xy = c^2
c^2 - 2xy = c^2 since x + y = c
2xy = 0
So, x = 0 or y = 0
When x = 0, y^2 = c^2
y = +/- c;
When y = 0, x^2 = c^2
x = +/- c


Finished, thank you~~~