Forbidden Equation

"Arrrggghh! Why is it so hard?!" Dan irritably blurted out, aggressively pulling and ruffling his hair. "Dad is going to kill me if I fail again in this grading period!" he continuously fussed, pacing his room. Currently, in his second year of college, calculus was Dan's ultimate kryptonite. He had failed the first half of the semester, resulting in a brutal beating from his father. While his older siblings had successfully graduated, established their own businesses, and carved out their paths, Dan was expected to seamlessly take over the family enterprise. The pressure was a suffocating weight on his shoulders. Naturally laid-back and averse to heavy responsibility, he found the mounting expectations agonizing to bear. Suddenly, his phone buzzed. It was Ted, his best friend and classmate, requesting a video call. Dan reluctantly answered. Ted's face immediately dominated the display, grinning wildly. "Zuppp, man! What you cookin'? Deyyymmn! You've been away for a week and missed a lot!" "What did I miss?" Dan asked, his forehead wrinkling into a deep frown. "Oh, well, our college belle got dumped by her so-called boyfriend. Our Math professor got relieved, and the one who replaced her is a bomb!" Ted answered, practically vibrating with excitement. Dan paused, a mental image of the cute classmate Ted was referring to—the campus belle—flashing in his mind. This was instantly followed by a vivid memory of her arrogant ex-boyfriend. Dan's face darkened, and a sullen expression took over. "Told you," Dan said, tightly clenching his fist. "I knew it from the start. That good-for-nothing dog was up to no good." "Yeah, yeah! That husky isn't even handsome. I wonder what Chell saw in him. He's such trash!" Ted remarked. "The professor got relieved, you said? Hmm..." Dan muttered, quickly changing the subject. "Yeah, she was heavily pregnant yet still attended school, pestering us all. It's good we can finally see a new face. Not that same woman who didn't even know how to smile and couldn't even teach well!" Dan complained, completely ignoring the fact that his friend had described the new substitute professor as an absolute bombshell. "Anyway, spare me your notes, man. Mom is surely going to check if I caught up on what I missed in class. I can't show her a blank answer sheet. She'll tell Dad, and I'll be completely doomed!" Ted laughed loudly. "Hahaha! What have you been doing these past days, man? I'm not buying your excuse of having a fever. Who gets a fever during summer?! Hahaha!" "Shut it, bro! I'm in a crisis here!" Dan snapped. "Just spare me the notes. Gotta go! I'll see you tomorrow in class!" "Oookkkiiieeee!" Ted answered, ending the video call. Seconds later, Dan's screen lit up with a series of photographs showing the missed class notes. He hurriedly copied them down, letting out heavy sighs as he worked late into the night.