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化简求值:(x+2y) 2 %(2x+y) 2 ,其中x=%2,y=1

解:原式=x﹣2x﹣4y+3y﹣6x=(1﹣2﹣6)x+(﹣4+3)y,=﹣7x﹣y.当x=﹣2,y=1时,﹣7x﹣y=﹣7×(﹣2)﹣1=14﹣1=13.

如图

解:(1)﹣3(2x 2 ﹣xy)+4(x 2 +xy﹣ )=﹣6x 2 +3xy+4x 2 +4xy﹣1)=﹣2x 2 +7xy﹣1,把x=﹣1,y=﹣ 代入﹣2x 2 +7xy﹣1=﹣2+1﹣1=﹣2.(2)∵|x﹣2|+(y+1) 2 =0,则x﹣2=0,x=2;y+1=0,y=﹣1.则﹣2(2x﹣3y 2 )+5(x﹣y 2 )﹣1=﹣4...

(3x2y-2xy2)-2(x2y-3xy2)-(3x2y-2xy2)=3x2y-2xy2-2x2y+6xy2-3x2y+2xy2)=-2x2y+6xy2,当x=-4,y=-12时,原式=-2×(-4)2×(-12)+6×(-4)×(?12) 2=16+(-6)=10.

3(x²+xy)-2(x³-y³-3xy)+(-3xy-2y³) =-2x³ + 3x² +6xy x=1 y=2代入 2+3+12=17

(1)原式=1-x?yx?2y?(x?2y)2(x?y)(x+y)=1-x?2yx+y=x+y?x+2yx+y=3yx+y,当x=2,y=5时,原式=3×52+5=157;(2)原式=(x+2)(x?2)+4(x?2)2?x?2x=x2(x?2)2?x?2x=xx?2,当x=-12时,原式=?12?12?2=15.

(x-4y-x-16y-8xy)÷4y=(-8xy-20y)÷4y=-(2x+5y)=-(-10+10)=0

(x^2y-2y^2-xy-1)-(2xy+4x^2-y^2)+3 =-3x²-y²-3xy+2 =-3×1-4-3×(-1)×(-2)+2 =-3-4-6+2 =-11; 请采纳 如果你认可我的回答,敬请及时采纳, ~如果你认可我的回答,请及时点击【采纳为满意回答】按钮 ~~手机提问的朋友在客户端右上角评价...

(x+y)(x-y)+(x-y)²-(6x²y-2xy²)÷2y =(x+y)(x-y)+(x-y)²-2xy(3x-y)÷2y =(x+y)(x-y)+(x-y)²-x(3x-y) =x^2-y^2+x^2-2xy+y^2-3x^2+xy =-x^2-xy =-x(x+y) =-(-2)(-2+1/3) = -10/3

1/4(-4x²+2x-8y)-(1/2x-2y) =-x²+x/2-2y-1/2x+2y =-x²+x/2-1/2x+2y-2y =-x² =-(-1/2)² =-1/4 经化简多项式的值与y 无关

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