求题目,希望能给你满意答复.平方差：X^2-Y^2=(X+Y)(X-Y)完全平方：X^2+2XY+Y^2=(X+Y)^2X^4-Y^4=(X^2+Y^2)(X^2-Y^2)=(X^2+Y^2)(X+Y)(X-Y)X^4+Y^4=(X^2+Y^2)^2-2X^2*Y^2 =(X^2+Y^2+根号2*XY)(X^2+Y^2-根号2*XY)根号下的4+2根号3=1+根号34除（3-根号5）=3+根号5