AI-verified
Every contribution passes a two-pass AI referee. The community confirms or challenges it here — so correctness is checked once and kept honest over time.
Community problem · Algebra · Telescoping
A product that collapses
Evaluate the product for .
Stuck? A gentle nudge
No hints for this one.
Your working
Check your full solution
Upload photos of your handwritten work or a PDF, and Lemma will read it and tell you whether it's right — and where it first goes wrong if not.