x²+y²=(x²+2xy+y²)-2xy=(x+y)²-2xy=2²-2×0.5=4-1=3(x-y)²=x²-2xy+y²=(x²+2xy+y²)-4xy=(x+y)²-4xy=2²-4×0.5=4-2=2很高兴为您解答,【the 1990】...