已知x=2-根号3,y=2+根号3，求下列代数式的值(1）x^2+2xy+y^2=(x+y)^2=(2-√3)(2+√3)^2=2^2=4(2)x^2-y^2=(x+y)(x-y)=(2-√3+2+√3)(2-√3-2-√3)=4×(-2√3)=-8√3
