Answer:
The system has unique solution.
Step-by-step explanation:
Since the system has two unknow variables and two equations, we can resolve for one variable in the first equation and replace in the second equation.
We have the system
[tex]x+y=4\\x-y=0[/tex]
We resolve for x in the first equation and obtain
[tex]x=4-y[/tex]
Now, replace in the second equation the value of x,
[tex](4-y)-y=0\\4-2y=0\\y=2[/tex]
Now, replace the value of y in the expression of x:
[tex]x=4-y=4-2=2[/tex]
Then the system has unique solution, (x,y)=(2,2)
