x+y=1 (x+y)^2=x^2+2xy+y^2=1 (x+y)^3=x^3+y^3+3xy(x+y)=1 而x^3+y^3=1/3,代入得：3xy=2/3 xy=2/9 由于x = 1 - y;故代入xy = 2/9;中得 y(1-y) = 2/9 = 1/3×(1-1/3);故y = 1/3;x = 1 - y =2/3;将x、y的值代入所求中...