已知代数式x²-3xy-4y²-x by-2能分解成
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(3x-4y+5xy)-(2x-3y)+5xy=3x-2x-4y+3y+5xy+5xy=x-y+10xy=3+4×10=43
(3x-4y+5xy)-(2x-3y)+5xy=3x-4y+5xy-2x+3y+5xy=(x-y)+10xy=3+50=53
解x+2y=2xy=12x+4y+3xy+1=2(x+2y)+3×1+1=2×2+3+1=4+4=8
原式=3xy+6y-xy+6x=2xy+6(x+y)=2*(-2)+6*4=24-4=20
(4xy+12y)+(7x-(3xy+4Y-x))=4xy+12y+(7x-3xy-4y+x)=4xy+12y+7x-3xy-4y+x=(4-3)xy+(12-4)y+(7+1)x=xy+8y+8x当
(-3xy—7y)+[4x—3(xy+y—2x)]=-3xy-7y+4x-3xy-3y+6x=-6xy-10y+10x=-6xy-10(x-y)=12-30=-18
24(3xy+10y)+[4x-2(3xy+2y-x)]=3xy+10y+4x-6xy-4y+2x=6x+6y-3xy=6(x+y)-3xy=6*3-3*(-2)=18+6=24
原式=6x+4xy+2xy+3x+2y-4xy+7y=9x+9y+2xy=9(x+y)+2xy=9×4+2×2=36+4=40
5xy+4x+7y+6x-3xy-4xy+3y=5xy-3xy-4xy+4x+6x+7y+3y=(5-3-4)xy+(4+6)x+(7+3)y=-2xy+10x+10y=-2xy+10(x+y)因为x
3xy+4x+2y=3xy+2(2x+y)=3*7+2*8=21+16=37
3(xy+2y)-(xy-6x)=3xy+6y-xy+6x=2xy+6(x+y)=2×(-2)+6×4=-4+24=20
根据题意,有x-4≥0,4-x≥0∴x-4=0x=4y=3∴原式=49*(-41/7)=-287
先把代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)化简(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)=5XY+4X+7Y+6X-3XY-4XY+3Y=-2XY+10X+1
原式=-2x^2-2y^2-3xy-11xy=-2*7-14*(-1)=0
(3x-4y+5xy)-(2x-3y-2xy)=3x-4y+5xy-2x+3y+2xy=x-y+7xy=4+7×(-2)=4-14=-10
解题思路:先合并同类项,再结合已知条件变形,代入数值进行计算解题过程:求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值解:(2x+3y-2xy)-(x+4+xy)-(3x
已知x+xy=-2,xy-y=-6则X+Y=42x{-4y-3[(x+xy)²+x]-½[(y-xy)²-2y]=2x{-4y-3[(-2)²+x]-&fr
(3x-4y+5xy)-(2x-3y)+5xy=3x-4y+5xy-2x+3y+5xy=x-y+10xy=3+10*5=53
∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6