a^2ｂ^2＋ｂ^2＋１＝４ａｂ－ａ^2 (a^2-2ab+b^2)+(a^2b^2-2ab+1)=0 (a-b)^2+(ab-1)^2=0 所以a=b=1或a=b=-1 a^3+b^3=+-2