Answer :
[tex]x+y=0 \\ x-y=10 \\\\
x=-y\\
x-y=10\\\\
-y-y=10\\
-2y=10\\
y=-5\\\\
x-5=0\\
x=5\\\\
\boxed{(x,y)=(5,-5)}[/tex]
x+y=0
- x-y=10
--------------
(0)+2y=-10 [x and -x cancel each other out. y minus -y is the same as y+y]
y=-5
now substitute -5 in for y in either problem:
x+-5=0
x=5
- x-y=10
--------------
(0)+2y=-10 [x and -x cancel each other out. y minus -y is the same as y+y]
y=-5
now substitute -5 in for y in either problem:
x+-5=0
x=5
