Answers

2014-03-08T20:13:41+05:30
The point a will always lie on the line,

y-a = m(x-a)

where m is the slope of the line
1 4 1
i took the general equation --- y-y1=m(x-x1)
2014-03-08T20:14:16+05:30
The point (a, a) always lies on the line : 

The point is (a,a)
taking the equ. x+y=0
putting x=a, y=a
=> L.H.S   x+y=a+a=2a=R.H.S
so point (a, a) lies on the equ. x+y=2a
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HOW CAN YOU TAKE THE EQUATION X+Y=0