已知方程组3x 2y=3,2x ay=1

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化简求值①化简:4ab+8-2b2-9ab-6②先化简,再求值:已知3x2y-[2x2y-3(2xy-x2y)-xy],

(1)4ab+8-2b2-9ab-6=-2b2-5ab+2(2)原式=3x2y-2x2y+6xy-3x2y+xy=-2x2y+7xy,当x=-1,y=-2时,原式=-2×(-1)2(-2)+7×(-1

已知向量a,b不平行,求满足向量等式3xa+(10-y)b=(4y+7)a+2xa的实数x,y

3xa+(10-y)b=(4y+7)a+2xa所以移项后合并同类项后得到:(x-4y-7)a+(10-y)b=0由于a和b不平行,所以x-4y-7=0且10-y=0所以x=47,y=10

先化简,再求值(3x2y-2xy2)-(xy2-2x2y),其中x=-1,y=2.

(3x2y-2xy2)-(xy2-2x2y)=3x2y-2xy2-xy2+2x2y=5x2y-3xy2当x=-1,y=2时,原式=5×(-1)2×2-3×(-1)×22=10+12=22.

已知A=x3-2y3+3x2y+xy2-3xy+4,B=y3-x3-4x2y-3xy-3xy2+3,C=y3+x2y+2

因为A+B+C=x3-2y3+3x2y+xy2-3xy+4+y3-x3-4x2y-3xy-3xy2+3+y3+x2y+2xy2+6xy-6=1,所以,对于x、y、z的任何值A+B+C是常数.

2(x2y+xy)-3(x2y+xy)-4x2y其中x=-2,y=12

原式=2x2y+2xy-3x2y-3xy-4x2y=-5x2y-xy当x=-2,y=12时,原式=-9.

先化简后求值:4x2y-[6xy-3(4xy-2)-x2y]+1,其中x=2,y=-12

原式=4x2y-6xy+3(4xy-2)+x2y+1=5x2y+6xy-5当x=2,y=-12时,原式=5×4×(-12)+6×2×(-12)-5=-21.

当x=2011,y=2012时,求代数式3x3-4x3y2+3x2y+2x2+4x3y2+2x2y-5x2-5x2y+x

化简得:9-12Y^2+6Y+4+12Y^2+4Y-10-10Y+X-Y+1=X-Y+4带入X、Y值得:=3

已知A=x3+3x2y-5xy2+6y3-1,B=y3+2xy2+x2y-2x3+2,C=x3-4x2y+3xy2-7y

A+B+C=(x3+3x2y-5xy2+6y3-1)+(y3+2xy2+x2y-2x3+2)+(x3-4x2y+3xy2-7y3+1)=(1+1-2)x3+(3+1-4)x2y+(-5+2+3)xy2

(X+Y)2=1402X2Y*3=14400

(X+Y)2=1402X2Y*3=14400(X+Y)2=140→X+Y=70→Y=70-X①2X2Y*3=14400→XY=1200②把①代人②得:X(70-X)=1200X²-70X+1

已知x,y,z满足(1)已知|x-2|+(y+3)2=0(2)z是最大的负整数化简求值2(x2y+xyz)-3(x2y-

|x-2|+(y+3)²=0都是非负式所以分别都=0所以x-2=0y+3=0所以x=2y=-3又因为z是最大的负整数所以z=-1原式=2(x²y+xyz)-3(x²y-x

(-2x2y)3*4x-3sup>=

题目1看不明白解题目2x+y=4,(x+y)^2=4^2=16,同样x-y=10,(x-y)^2=10^2=100,(x+y)^2=x^2+2xy+y^2,(x-y)^2=x^2-2xy+y^2,(x

4x2y-{x2y-「3xy2 – 1/ 2(4x2y-8xy2)+x2y」}-5xy2

答案:2x^2y+2xy^2原式=4x2y-{x2y-[3xy2-2x2y+4xy2+x2y]}-5xy2=4x2y-{x2y-[7xy2-x2y]}-5xy2=4x2y-{x2y-7xy+x2y]}

已知a方-a-1=0,求2a四次方-3xa方+2/a立方+2xa-a=-93/112 x=?

a^2-a-1=0a^2-1=aa^2=a+1(2a^4-3xa^2+2)/(a^3+2xa^2-a)=-93/112(2a^4-3xa^2+2)/(a^3+2xa^2-a)=[a^2(2a^2-3x

已知(x-2)2+|y+1|=0,求5xy2-[2x2y-(3xy2-2x2y)]的值.

原式=5xy2-2x2y+3xy2-2x2y=8xy2-4x2y,∵(x-2)2+|y+1|=0,∴x-2=0,y+1=0,即x=2,y=-1,则原式=16+16=32.

数学竞赛题:若实数x,y满足方程组xy+x+y+7=0,3x+3y=9+2xy,则x2y+xy2=?

x2y+xy2=xy*(x+y)因为x+y=-(7+xy)又x+y=(9+2xy)\3所以(9+2xy)\3=-(7+xy)3+2xy\3=-7-xy5xy\3=-10解得xy=-6所以x+y=-(7

当x=-1,y=1时求代数式2x2y-(5xy2-3x2y)-x2的值

代入x=-1,y=1,2x^y-(5xy^-3x^y)-x^=2*(-1)^*1-{5*(-1)*1^-3*(-1)^*1}-(-1)^=2-(-5-3)-1=9备注:2^表示2的平方

化简求值:2(x2y+xy)-3(x2y-xy)-4x2y,其中x=-1,y=1.

原式=2x2y+2xy-3x2y+3xy-4x2y=-5x2y+5xy,当x=-1,y=1时,原式=-5×(-1)2×1+5×(-1)×1=-5-5=-10.

关于x,y的方程组 3x+2y=m+1,4x2y=m-1求y,x

如果x,y符号相反,绝对值相等,即y=-x,代入原方程组,得3x-2x=m+1,4x-2x=m-1,即x=m+1,2x=m-1解之,2(m+1)=m-1,得m=-3如果x比y大1,即x=y+1,代入原

已知A=8x2y-6xy2-3xy,B=7xy2-2xy+5x2y,若A+B-3C=0,求C-A.

由题意得:3C=A+B=8x2y-6xy2-3xy+7xy2-2xy+5x2y=13x2y+xy2-5xy,∴C=13x2y+xy2−5xy3,故:C-A=13x2y+xy2−5xy3-(8x2y-6

已知xn=5,yn=3,求:(1)(x2y)2n;(2)x3n÷y4n.

(1)∵xn=5,yn=3,∴(x2y)2n=x4ny2n=(xn)4(yn)2=54×32=5625;(2)∵xn=5,yn=3,∴x3n÷y4n=(xn)3÷(yn)4=53÷34=12581.