(a+b)^n=C(n,0)a^n+C(n,1)a^(n-1)*b+C(n,2)a^(n-2)*b^2+...+C(n,n)b^n是二项试定理.给隐旅晌个网址你看灶锋看镇衡http://www.huanggao.net/course/40430/SX_22_02_012_L/
http://baike.baidu.com/view/392493.htm
(a+b)^n=C(n,0)a^n+C(n,1)a^(n-1)*b+C(n,2)a^(n-2)*b^2+...+C(n,n)b^n