45 in a 40? That's a pretty chicken-shit ticket. Here in California that most likely wouldn't hold up in court, as the law (CVC 22350) states that unless you're exceeding 65mph, or in a "prima facia" speed limit location (school zone or business district, which are 25 and 35mph respectively) the "prosecution" (or Officer in this case) has to prove that your speed (45mph in this case) was too dangerous for the conditions.

In other words, giving a citation for 45mph in a 40mph, while traveling downhill in a relatively low population area, is not going to be deemed "unsafe for conditions" and thus would be thrown out.

Not sure if that's the way it works in your state -- but that's how it works in California.

That said, even if your state, you should be eligible for traffic school.

My record looks like:
92 in a 65 when I was 16.
88 in a 65 when I was 19.

Did traffic school for the 92, didn't for the 88.