Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic applies mathematical reasoning to the common romantic expression "I love you more each and every day." A man sits in a cafe, noticing a woman scowling at him and wondering if he knows her. The caption below delivers the punchline: "If she loves you more each and every day, by linear regression she hated you before you met."

The joke takes the sentimental cliché literally and extends the implied linear trend backward in time. If love increases at a constant daily rate starting from when you met, then extrapolating the line into the past would place its value below zero before the relationship began -- meaning she must have hated you before she even knew you existed. The scowling stranger in the comic is the visual embodiment of this mathematical absurdity, a woman who apparently already hates a man she has never met, perfectly consistent with the linear model.