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求解答过程:先化简,再求值:[(x+2y)²-(x+y)(3x-y)-5y²]÷2x,其中...
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回答:原式=x^2-4y^2+2x^2-5xy-3y^2-4x^2+4xy-y^2 =-x^2-xy-8y^2 =(-1)^2-(-|)x2-8x2^2 =-29
原式=x²-4y²-(9xy+3x²-xy)+8xy =x²-4y²-(3x²+8xy)+8xy =x²-4y²-3x²-8xy+8xy =-2x²-4y²将x,y的值代入即可
原式=(x²-4y²-x²-8xy-16y²)(-2y)=(-8xy-20y²)(-2y)=16xy²+40y³=320+320 =640
(x+2y)2-x-y-3x+y-5y2/2x 3x-x+x 2sadasdsadasd
(x+2y)^2-2(x-y)(x+y)+2y(x-3y)=x^2+4xy+4y^2-2x^2+2y^2+2xy-6y^2---展开 =-x^2+6xy---合并同类项 =-4-6*2*1/2---代入求解 -10
原式=x2+4xy+4y2-(x2-4y2)=x2+4xy+4y2-x2+4y2=4xy+8y2,当x=12,y=-2时,原式=-4+32=28.
原式 =[(x+2y)^2-x^2+2xy]/(2y)=[(x+2y+x)(x+2y-x)+2xy]/(2y)=[2y(2x+2y)+2xy]/(2y)=(2x+2y)+x =3x+2y =3×(-2/3)+2×5 =-2+10 =8。
原式=x2+2xy-(x2+2x+1)+2x=x2+2xy-x2-2x-1+2x=2xy-1,把x=13,y=?3代入,得原式=2xy-1=2×13×(-3)-1=-3.
解:① =﹣1+(﹣8)× ﹣(﹣3)×(﹣ )=﹣1+(﹣1)﹣1=﹣3;②[(x+2y)(x﹣2y)﹣(x+4y) 2 ]÷4y=[x 2 ﹣4y 2 ﹣x 2 ﹣16y 2 ﹣8xy]÷4y=(﹣20y 2 ﹣8xy)÷4y=﹣5y﹣2x将x=5,y=2代入上式得,原式=﹣5y﹣2x=﹣5×2﹣2×5=﹣10﹣10=﹣20。
一、x-y/x+2y除x²-y²/x²+4xy+4xy²-2其中x=2+√3,y=2√3 解:原式=(x-y)/(X+2Y)×(X+2Y)²/[(X+Y)(X-Y)]-2 =(X+2Y)/(X+Y)-2 =(-X-3Y)/(X+Y)当X=2+√3,Y=2√3时,原式=(-2-7√3)/(2+3√3)=-(2+7√3)(3√...