$(x+y)^2=x^2+2xy+y^2$
 $(x+y)^3=x^3+3x^2y+3xy^2+y^3$
 $(x+y)^n=x^n+nx^{n-1}y+\frac{n(n-1)}{2}x^{n-2}y^2+\cdots+\binom{n}{k}x^{n-k}y^k+\cdots+nxy^{n-1}+y^n$
where
 ${n \choose k}=\frac{n(n-1)\cdots(n-k+1)}{1\cdot 2\cdot 3\cdot \cdots \cdot k}$
([[조합,combination]])
(Stewart 9e 맨 앞)

'''[[이항정리,binomial_theorem]]''' [[이항계수,binomial_coefficient]] 관련

MKLINK
[[이항급수,binomial_series]] ... (writing) curr at [[급수,series#s-2]], tmp see WpKo:이항_급수 WpEn:Binomial_series Naver:이항급수

Up: [[전개,expansion]]