①(x+y)²=x²+y²+2xy
x²+y²=(x+y)²-4xy
=(-5)²-4×6
=25-24
=1
②(x-y)²=x²+y²-2xy
x²+y²=(x-y)²+4xy
=(-5)²+4×6
=25+24
=49