Question

Is point (2,1) on the the line represented by the equation x+2y=5

Answer 1

(x,y)
(2,1)
that means x=2 and y=1 is true, or is it?
just subsitute 2 for x and 1 for y and see if you get a true statement

2+2(1)=5
2+2=5
4=5
false
it is not on the line

Answer 2

To check if this point lies on the line, plug in a 2 for x and a y for 1 and solve

x+2y=5
2+2(1)=5
4=5

Since this statement isn't true, then the point doesn't lie on the line

Hope this helps