Disclaimer: Numb3rs and its associated characters, locales, etc. is the property of CBS and the people who make it, and its material is used here without permission; no copyright infringement is intended, and the author asks anyone who takes issue to its use here to contact her.

A/N: This is a short piece, probably a one-shot. I started it with a big long story behind it, but have lost my desire to write that story at the moment, as I'm all involved in writing another. So I'm posting this as is; if I ever get around to writing the rest, I'll post it. So as it stands it's just a bit of a character piece. Also, I get annoyed that we never seem to get to see Charlie teaching, though it's essentially his job, so I wanted to write some of it.

Rating: K+ for one instance of slightly strong language

Credit where Credit is due: Find the definition of a function at http/mathworld.wolfram. com/Function.html . I took Math 110 a few years ago; remember none of it!

Math 110A

by Deichtine

Don entered the lecture theatre as quietly as he could, and slipped into a seat near the back behind a pair of giggling freshmen girls. He had gotten off work early and arrived to pick up Charlie about forty-five minutes too soon. When he arrived he found Charlie still in class and, after a few moments indecision standing outside the door, made up his mind to go on in and sit through what was left of his brother's class.

From where he slouched in his seat, Don could see Charlie clearly over the multicolored sea of heads, his curly brown hair bobbing lightly as his right arm worked furiously to cover the blackboard at the front of the room with writing.

It was the beginning of the semester, and the last class of the day for Charlie was Math 110A, an introduction to calculus for students who did not intend to pursue math as a major, but needed a credit or a basic grounding. Don had overheard Charlie groaning about having to take on the class overtop of an already full load; an assistant professor had suddenly left on stress leave shortly before the semester's beginning, and the administration often gave Charlie some of the freshmen classes hoping that the students would identify with him due to his youth.

Don also knew that it was not really the workload that he disliked, nor the students, but rather the frustration of having to explain what he saw so clearly to those who just didn't see it. He had described the feeling once. "Let me put it this way, Don. Have you ever tried to show Dad how to send an email? You have to start with the power button, turning the computer on, tell him that everything's okay when Windows is loading and the splash screen doesn't seem to be doing anything, explain how to open the email program, then how email works...you know what I'm talking about? Now take that feeling and multiply it by a hundred." It had since become an in-joke between them; when Charlie was frustrated with having to 'dumb things down', he referred to it as 'sending Dad email'.

But for all the complaining he'd done, when Charlie turned around, Don saw none of that frustration in his brother's bearing. The younger Eppes was energetic, enthusiastically explaining the subject matter, his dark eyes bright.

"Today we're going to do a very fast review of the concept of the function. The function is one of the essential topics in algebra and forms the basis for calculus. I know many of you will have taken this in high school, but I also know that many of you will have forgotten. Am I right?" He smiled out at the crowd, and got a wave of nods and smiles in return. "Now, it's imperative you understand this before we go on to limits, so please, stop me if you have a question. Now, " Charlie turned back to the board, and began to scrawl rapidly, "A function is defined as a relation that uniquely associates members of one set with members of another set, or in more formal terms..."

Don sat back and just watched Charlie. His younger brother was an animal in its natural habitat; he fit in front of that class in a way Don had never seen him before. He didn't seem be referring to notes, but instead was just pulling equations and definitions out of his head as he went. He was relaxed and obviously enjoying himself, making jokes with the class where he could and once or twice venturing slightly off topic to bring in a reference to the real-world applications of the concepts he was talking about.

Don found himself becoming interested in spite of himself. Unlike the heady ultra-mathematics (as Don privately called it) that Charlie often used in his consultations with the FBI, this was material Don could understand at a pace he could follow, and he actually began to enjoy himself.

Immediately in front of Don, one of the blond students leaned over to her friend beside her, and Don could hear them talking. "I'm so glad we got Dr. Eppes this semester. I mean, I've got nothing against Granger, but Eppes is so cute."

The other girl nodded. "Totally. I mean, look at those eyes, and that curly hair? It's worth having to take Calculus, with a prof like him."

Don blinked.

The first rolled her eyes. "Almost worth it. His hair looks so soft. I bet he conditions. And that bod, all lean and - Oh, wait, look - "

"Wait for it..." the other giggled.

When the first girl finally said what she was looking at, Don tried to muffle a snort of laughter behind his hand, but failed. Charlie turned around, and peered out into the crowd, never stopping the verbal stream of explanation. His gaze fixed on Don, and he stopped, startled. He glanced at his watch.

"Yes, well, I think that's all we're going to get out of functions for today. You guys are starting to get that glazed look I know so well, so I think we'd better finish up." A wave of gentle laughter ran through the room. "For Thursday I want you to go online to the CalSci math department's web site and work through some of the pre-calculus algebra refresher course material. You know where your weaknesses are. Next class we're going to start on limits.

"Speaking of which, before you go, I want to introduce you to someone. Don, would you come down here, please?"

Don sat up straight. Had he heard that right? Was Charlie talking to him? Yes, his brother was looking right at him, one eyebrow raised good-humoredly. Feeling his face redden, he stood up and, tucking his coat over his harm, made his way down to the front of the room.

Charlie reached out to put a hand on his brother's somewhat tense shoulder. "This is my older brother, Special Agent Don Eppes of the Federal Bureau of Investigation." An impressed murmer rippled across the classroom. Don gave an uncomfortable little wave. "I'm embarrassing him like this for a reason. I was trying to explain earlier about how the concepts you learn here can be applied to the real world. Well, Don here provides a good example. I do consulting work with Don's office sometimes, helping them to gather evidence for cases using mathematical principles - equations based on the very same principles we were talking about today."

Don smiled, recovering a bit. "That's true. Charlie - Dr. Eppes, I should say - has proved an invaluable aid to our investigations on several occasions. When we were growing up I always thought math was a waste of time, all that theory with no real use to it, but your prof has shown me that there's a lot more to it."

A kid near the front called out, "Can we see your badge?"

Don held it up dutifully.

A girl - Don recognized her as one of the ones who had been admiring Charlie earlier, raised her hand. "What kind of cases does he help you with?" She was obviously entranced by the idea.

Don shrugged, and decided to give them what they wanted - the drama. "Serial murders, sometimes. Fraud. Kidnapping," he said, deadpan.

Charlie grinned. "And if you're all very good, at the end of the semester I'll show you some of the techniques I've developed for the FBI - once we've learned enough Calculus to understand it. Now go home, people! Class dismissed."

As the class began to empty, Don scowled at Charlie exaggeratedly. "What the heck was that all about?"

Charlie smiled and began to clean the blackboard. "Exactly what I said. Most of these kids don't really want to be there, they just need the math credit. Probably about thirty-five to forty per cent of them will fail unless I find a way to keep them interested and trying. Providing evidence of real-world applications is a good motivator." Charlie stopped erasing for a second, grinned at his brother. "Plus, it adds to my rep as the coolest math professor around, to have an FBI agent come visit class."

Don laughed aloud. "Cool math professor? I thought that was an oxymoron."

Charlie gave him an exaggerated mock-hurt expression. "You cut me to the quick, Don. What are you doing here, anyway? I thought I was going to meet you back at my office?"

"I got here early, thought I'd come and see what all the fuss was about, catch 'Dr. Eppes' in action."


"What scares me is that I think I was starting to understand this stuff." Don gestured vaguely at the blackboard, where equations were rapidly disappearing under Charlie's chalkbrush.

Charlie grinned. "If you want, I can go into it in more depth for you when we get home," he offered.

Don shook his head. "No, my poor brain's worked hard enough today, thank you."

Charlie put down the chalkbrush, brushed off his hands, and allowed Don to lead him from the classroom. When they broke out of the Math building into the late afternoon sunlight, Charlie skipped forward a few steps to fall in beside his older brother. "Hey Don," he said, thoughtfully.


"Back there in class, you laughed at something, that's how I noticed you. What were you laughing at? I have a feeling it wasn't my joke about 'dys-function-al' equation families."

Don tried very hard to maintain a straight face, and failed. "Actually, I got a bit of an inside look at why the freshmen love Dr. Eppes."

Charlie raised his eyebrows, now honestly interested; his mind was returning to the conversation he'd had with Larry about course evaluations, just before finding poor Finn's body. "Really? What is it? Maybe it will help Larry."

Don now could no longer contain his laughter. "I doubt it. You know the girl who asked about what kinds of assignments you help me with at the office?" Charlie nodded. "Well, I was sitting right behind her, and I could hear her talking to her friend about how happy they were to have got you as a prof."

Charlie beamed with pleasure. "I guess I'm a better teacher than I thought," he smiled. "What did she say?"

Don looked at his brother from the corner of his eye. "Her exact words?"

Charlie nodded.

"She said you have, and I quote, a 'damn fine ass.'"

What Don wouldn't have paid for a camera to capture the look on his brother's face.

The end for now.