作业帮(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!前面还有 忘打了 已知x,y满足:x二次方+y二次方-4x+6y+13=0
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(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!前面还有 忘打了 已知x,y满足:x二次方+y二次方-4x+6y+13=0
(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!
前面还有 忘打了
已知x,y满足:x二次方+y二次方-4x+6y+13=0
(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!前面还有 忘打了 已知x,y满足:x二次方+y二次方-4x+6y+13=0
x二次方+y二次方-4x+6y+13=0
(x-2)²+(y+3)²=0
则有：
x-2=0
y+3=0
解得：x=2；y=-3
(3x+y)²-3(3x-y)(x+y)-(x-3y)(x+2y)
=9x²+6xy+y²-3(3x²+2xy-y²)-(x²-xy-6y²)
=9x²+6xy+y²-9x²-6xy+3y²-x²+xy+6y²
=-x²+xy+10y²
=-4-6+90
=80
x^2+y^2-4x+6y+13=0
x^2-4x+4+y^2+6y+9=0
(x-2)^2+(y+3)^2=0
(x-2)^2=0,(y+3)^2=0
x=2
y=-3
(3x+y)^2-3(3x-y)(x+y)-(x-2y)(x+3y)
=9x^2+6xy+y^2-3(3x^2+2xy-y^2)-(x^2+xy-6y^2)
=9x...
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x^2+y^2-4x+6y+13=0
x^2-4x+4+y^2+6y+9=0
(x-2)^2+(y+3)^2=0
(x-2)^2=0,(y+3)^2=0
x=2
y=-3
(3x+y)^2-3(3x-y)(x+y)-(x-2y)(x+3y)
=9x^2+6xy+y^2-3(3x^2+2xy-y^2)-(x^2+xy-6y^2)
=9x^2+6xy+y^2-9x^2-6xy+3y^2-x^2-xy+6y^2
=9x^2-9x^2-x^2+6xy-6xy-xy+y^2+3y^2+6y^2
=-x^2-xy+10y^2
=-2^2-2*(-3)+10*(-3)^2
=-4+6+90
=92
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