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(3x+y)二次方-3(3x-y)(x+y)-(x-2y)(x+3y)要过程!

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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!
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
再问: 化简的式子打错了 是 (3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y)
再答: (3x+y)²-3(3x-y)(x+y)-(x-3y)(x+3y) =9x²+6xy+y²-3(3x²+2xy-y²)-(x²-9y²) =9x²+6xy+y²-9x²-6xy+3y²-x²+9y² =-x²+13y² =-4+13×9 =113