The slope of two parallel lines must be the same; if the slopes of two lines are the same then they must be parallel.
If line y=mx+2 and line y=3x+3 are parallel, what is the value of m?
Answer: Since the slope of two parallel lines must be the same, m=3.
Line 1 in point slope form is y=4x+5 and line 2 is y-9=4(x-7). Are these two lines parallel?
Answer: Yes. Line one is in point slope form y=mx+b, slope m=4.
Line two is in the form (y-y1)=m(x-x1), slope m=4, identical slope means they are parallel.