The
y
terms already have their coefficients the same with opposite signs. This means that if the two equations are added, the
y
terms will be eliminated.
(
+
2
y
)
+
(
−
2
y
)
=
0
Re-arrange the equations, then add them
−
4
x
+
2
y
=
−
10
..................................A
+
2
x
−
2
y
=
+
7
−−−−−−−−−−−−−−−
......................................B
−
2
x
=
−
3
x
=
3
2
Now substitute into A to find
y
−
4
(
3
2
)
+
2
y
=
−
10
−
6
+
2
y
=
−
10
2
y
=
−
4
y
=
−
2
Check in B:
2
(
3
2
)
−
2
(
−
2
)
=
3
+
4
=
7
