What's the difference between graphing and equality with a closed dot and one with an open dot

Hannah works at the mall selling book bags. she sold 35 book bags in 5 hours. how many book bags did she sell per hour?

1- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis.2- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in the first question?

Ab and bc form a right angle at point b. if a= (-3,-1) and b= (4,4) what is the equation of bc?