From graph, co-ordinates (1, -1) and (-1, 1) are solutions of one of the equations.
We will put the value of all the co-ordinates in each equation and check which equation satisfy them.
(i) y = x
Put x = 1 and y = -1,
Thus, 1 ≠ -1
L.H.S ≠ R.H.S
Putting x = -1 and y = 1,
-1 ≠ 1
L.H.S ≠ R.H.S
Therefore, y = x does not represent the graph in the given figure.
(ii) x + y = 0
Putting x = 1 and y = -1,
⇒ 1 + (-1) = 0
⇒ 0 = 0
L.H.S = R.H.S
Putting x = -1 and y = 1,
(-1) + 1 = 0
0 = 0
L.H.S = R.H.S
Thus, the given solutions satisfy this equation.
(iii) y = 2x
Putting x = 1 and y = -1
-1 = 2 (Not True)
Putting x = -1 and y = 1
1 = -2 (Not True)
Thus, the given solutions does not satisfy this equation.
(iv) 2 + 3y = 7x
Putting x = 1 and y = -1
2 – 3 = 7
-1 = 7 (Not true)
Putting x = -1 and y = 1
2 + 3 = -7
5 = -7 (Not True)
Thus, the given solutions does not satisfy this equation.
