How do you decide whether the graphs of the two equations are parallel lines: #y=2x-1, y=-2x+1#?
Lines are parallel, if their slope is same.
Slope of y= 2x-1 is 2
Slope of y= -2x+1 is -2.
The slopes are not same (not equal), hence lines are not parallel
Both lines are expressed in slope intercept form
To be parallel they would have to have the same slope. This is not the case so they are not parallel.
More in detail if the two lines
were parallel, then
and it is also obvious that the two lines cross for