x=2根号3+1
y=2根号3-1
x²-4xy+y²=x²-2xy+y²-2xy=(x-y)²-2xy
=[(2根号3+1-(2根号3-1)]²-2*(2根号3+1)*(2根号3-1)
=2²-2*[(2根号3)²-1]
=4-2*(12-1)
=-18
x=2根号3+1
y=2根号3-1
x²-4xy+y²=x²-2xy+y²-2xy=(x-y)²-2xy
=[(2根号3+1-(2根号3-1)]²-2*(2根号3+1)*(2根号3-1)
=2²-2*[(2根号3)²-1]
=4-2*(12-1)
=-18