几道数学题..关于十字相乘法的.求解..最好写出过程..1.(x+y)²-4(x+y)+82.(x+y)²+3(x+y)-283. x²y²-5xy+44. x²y²+6xy+85. x的三次方+5x²+6x

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几道数学题..关于十字相乘法的.求解..最好写出过程..1.(x+y)²-4(x+y)+82.(x+y)²+3(x+y)-283. x²y²-5xy+44. x²y²+6xy+85. x的三次方+5x²+6x
几道数学题..关于十字相乘法的.求解..最好写出过程..
1.(x+y)²-4(x+y)+8
2.(x+y)²+3(x+y)-28
3. x²y²-5xy+4
4. x²y²+6xy+8
5. x的三次方+5x²+6x

几道数学题..关于十字相乘法的.求解..最好写出过程..1.(x+y)²-4(x+y)+82.(x+y)²+3(x+y)-283. x²y²-5xy+44. x²y²+6xy+85. x的三次方+5x²+6x
1、=(x+y)^2-4(x+y)+4+4=[(x+y)-2]^2+4
2、=(x+y)^2+3(x+y)+(-4*7)=[(x+y)-4]*[(x+y)+7]
3、=(xy-1)(xy-4)
4、=(xy+2)(xy+4)
5、=x(x^2+5x+6)=x(x+3)(x+2)