Can Parents One A+ And Other O+ Make A A- Baby?

A person only has type O blood if they got one O from each parent. If you get an O from one parent and an A from the other, you'll have type A blood. So an O parent and an A parent with A kids will have received one O and one A, making them have type A.
Negative Rh works like type O, so that the only way to have negative blood type is to receive the negative gene from both parents.
This means that even though your blood type looks like O+, what you actually got from your parents (and have the ability to pass to your kids) is OO+-. That is, a positive blood type can actually pass on a positive or negative blood type. A negative blood type, however, only can pass on negative.
So, someone with a A+ blood type can pass on A or O blood that is positive or negative.