（a+1）^2-(3a^2+4ab+4b^2+2) =a^2+2a+1-3a^2-4ab-4b^2-2 =-2a^2+2a-1-4ab-4b^2=0 所以2a^2-2a+1+4ab+4b^2=0 (a^2-2a+1)+(a^2+4ab+4b^2)=0 (a-1)^2+(a+2b)^2=0 因为(a-1)^2>=0,(a+2b)^2>=0 所以a-1=0,a+2b=0...