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6x 2 xy 2y 2 2x 8y 8

原式=(2x-y)(3x+2y)+2x-8y-8 2x-y -2 × 3x+2y 4 x系数-6+8=2 y系数-4-4=-8、 原式=(2x-y-2)(3x+2y+4)

原式=3x(2x-y-2)+3xy+6x+xy-2y2+2x-8y-8=3x(2x-y-2)+4xy-2y2+8x-8y-8=3x(2x-y-2)+2y(2x-y-2)+2y2+4y-2y2+8x-8y-8=3x(2x-y-2)+2y(2x-y-2)+8x-4y-8=3x(2x-y-2)+2y(2x-y-2)+4(2x-y-2)=(2x-y-2)(3x+2y+4)

原式=12x2-18xy+24y2-12x2+21xy-24y2=(12x2-12x2)+(-18xy+21xy)+(24y2-24y2)=3xy,当x=73,y=-5时,原式=3×73×(-5)=-35.

(1) -3+(-x^2+4x)-(-8+3x^2) =-3-x2+4x+8-3x2 =5+4x-4x2(2)-1/2(4xy-8x^2 y^2)+1/3(xy-6x^2 y^2) =-2xy+4x2y2+xy/3-2x2y2 =-5xy/3+2x2y2

双十字相乘

方程应该是:-x³+6x²y-12xy²+8y³=0(8y³项前不应是=号,具推猜应该是+号) 将方和整理成::x³-6x²y+12xy²-8y³=0 方程两边都除以y³,整理后得:(x/y)³-6(x/y)²+12(x/y)-8=0 令x/y=...

原式=[6x3y+6x2y2-3x3y+3x2y2]÷3x2y=(3x3y+9x2y2)÷3x2y=3x3y÷3x2y+9x2y2÷3x2y=x+3y.

(x-2y)^2 =x^2+4y^2-4xy 25=x^2+4y^2+8 x^2+4y^2=17 (x+2y)^2 =x^2+4xy+4y^2 =17-8 =9 后面一题请检查下

/x/=三分之八,/y/=四分之十五,且xy

6x^2+xy-2y^2=0 (2x-y)(3x+2y)=0 x=y/2 or x= -2y/3 x/y = 1/2 or -2/3

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