A=x2+xy-y2,B=-x2-2xy+y2,当x=1,y=1时,求2a-b的值x2代表x的二次方y2等也代表二次方

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A=x2+xy-y2,B=-x2-2xy+y2,当x=1,y=1时,求2a-b的值x2代表x的二次方y2等也代表二次方
A=x2+xy-y2,B=-x2-2xy+y2,当x=1,y=1时,求2a-b的值
x2代表x的二次方
y2等也代表二次方

A=x2+xy-y2,B=-x2-2xy+y2,当x=1,y=1时,求2a-b的值x2代表x的二次方y2等也代表二次方
2A-B
=2（x²+xy-y²）-(-x²-2xy+y²)
=2x²+2xy-2y²+x²+2xy-y²
=3x²+4xy-3y²
=3*1²+4*1*1-3*1²
=3+4-3
=4

2a-b=2（x2+xy-y2）-（-x2-2xy+y2）
=2x2+2xy-2y2+x2+2xy-y2
=3x2+4xy-3y2
=3+4-3
=4

(x2-2xy+y2)-(x2+2xy+y2)=什么已知A=x2-xy+y2,B=-x2+2xy+y2求A+B A-B 若X2+xy-2y2=0,则（x2+3xy+y2)/x2+y2=? 若A=x2-xy-y2,B=-2xy-3y2,则2A-3B=_____ 已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2= 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2. x2+y2+2xy=256 x2+y2-2xy=4 (x2, x2-3y2=2xy过程已知整式A=2x2-3xy+2y2,B=2x2+xy-3y2 (1)求A+B （2)求2A-3B 已知A=x2-3xy+y2,B=3x2-xy+3y2,适用A与B来表示x2+y2 若A=X2-xy,B=xy+y2,则A×B= A=3x2+3y2-5xy,B=2xy-3y2+4x2,求：（1）2A-B；解方程组 x2 -2xy -y2 =1 2x2 -5xy -3y2 =0 解方程组 x2+2xy+y2-4=0 x2-2xy+y2-1=0 已知X2次方+XY=3,XY+Y2次方=-2,求下例值:X2次方-Y2次方 x2+3xy+2y2=0,则x2+y2/xy X2+Y2+XY=2,求X2+Y2-XY取值范围分解因式(x2+xy+y2)2-4xy(x2+y2)=?