已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x&
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已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.
(1)x²-y²
=(x²+xy)-(xy+y²)
=3-(-2)
=5
(2)x²+4xy+3y²
=(x²+xy)+3(xy+y²)
=3+3×(-2)
=3-6
=-3
(3)2x²-xy-3y²
=2(x²+xy)-3(xy+y²)
=2×3-3×(-3)
=6+9
=15 再答: ��1��x²��y² =(x²+xy)-(xy+y²) =3-(-2) =5 ��2��x²+4xy+3y² =(x²+xy)+3(xy+y²) =3+3��(-2) =3-6 =-3 ��3��2x²��xy��3y² =2(x²+xy)-3(xy+y²) =2��3-3��(-2) =6+6 =12 (ǰ�濴����һ�����֣��Ǻ�)
=(x²+xy)-(xy+y²)
=3-(-2)
=5
(2)x²+4xy+3y²
=(x²+xy)+3(xy+y²)
=3+3×(-2)
=3-6
=-3
(3)2x²-xy-3y²
=2(x²+xy)-3(xy+y²)
=2×3-3×(-3)
=6+9
=15 再答: ��1��x²��y² =(x²+xy)-(xy+y²) =3-(-2) =5 ��2��x²+4xy+3y² =(x²+xy)+3(xy+y²) =3+3��(-2) =3-6 =-3 ��3��2x²��xy��3y² =2(x²+xy)-3(xy+y²) =2��3-3��(-2) =6+6 =12 (ǰ�濴����һ�����֣��Ǻ�)
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