已知x-y=2,xy=-½,求x²+y²的值.
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已知x-y=2,xy=-½,求x²+y²的值.
已知x-y=2,xy=-½,求x²+y²的值.
已知x-y=2,xy=-½,求x²+y²的值.
x²+y²
=(x²-2xy+y²)+2xy
=(x-y)²+2xy
=(2)²+2×(-1/2)
=4-1
=3
x²+y²
=(x-y)²+2xy
=2²+2*(-1/2)
=4-1
=3
x²+y²=x²+y²-2xy+2xy=(x-y)²+2xy=4-1=3
=(x-y)²+2xy=4+(-1)=3