i hope my handwriting isnt too bad and that this helps!
I hope this helps you
-x+4=2x+1
4-1=2x+x
3=3x
x=1
y=-1+4
y=3
Use photos math it helps alot
The relation is <em>not a function</em> if any x-value is repeated.
Assuming you have
(x, y) = (3, 10), (__, 20)
if x = 3, the relation is not a function.