Toolkit 23SFFT (Simon's Favorite Factoring Trick)xy+ax+by=c ⇒ (x+b)(y+a)=c+abxy+ax+by=c\;\Rightarrow\;(x+b)(y+a)=c+abxy+ax+by=c⇒(x+b)(y+a)=c+abGSFFT (General Form)\text{GSFFT (General Form)}GSFFT (General Form)axy+bx+cy=daxy+bx+cy=daxy+bx+cy=da2xy+abx+acy=ada^2xy+abx+acy=ada2xy+abx+acy=ad(ax+c)(ay+b)=ad+bc(ax+c)(ay+b)=ad+bc(ax+c)(ay+b)=ad+bcRelated ProblemsCoreSMO 2025 Junior (Problem 8)AIME I 2026 (Problem 4)