Solve and Graph the Inequalities​

we know that

If two lines are parallel, then their slopes are the same

m1=m2

and the y-intercept is unequal

If two lines are perpendicular, then the product of their slopes is equal to -1

m1*m2=-1  or m1=-1/m2

therefore

the answer is

Two non vertical lines have slopes m1 and m2​, respectively. The lines are parallel if​ m1=m2 and the ​y-intercept are​ unequal; the lines are perpendicular if​ m1*m2=-1 or​ m1=-1/m2.