Generalised form of the equation
$$y=mx$$
So, from the graph we have seen that for a linear equation given by the equation $y=mx+c$ where $m=1$, the line is a straight line passing through the origin and making an angle of 45o with the horizontal axis.
Note:Since $m$ is the slope of the line , therefore if $m$>1, then the line will make angle greater than 45o with the horizontal axis and if $m$<1 , then the line will make angle less than 45o with the horizontal axis. (because tan(45degree) = 1 )
(0,0)
(2,2)
(-1,-1)
(1,1)