用杨辉三角形直接分解(1+√x)^5和(1-√x)^5(1+√x)^5=1+5√x+10√x^2+10√x^3+5√x^4+√x^5(1-√x)^5=1-5√x+10√x^2-10√x^3+5√x^4-√x^5(1+√x)^5+(1-√x)^5(√x的奇次项相抵消,得√x的偶次项)=2+20x+10x^2...