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化简:(1)2(2a-3b)+3(2b-3a)(2)2(x2-xy)...

(1)原式=4xy-3x2+3xy-2y+2x2=7xy-x2-2y;(2)原式=a+b-4a+6b+3a-2b=5b;(3)原式=-13x-23y+23y=-13x,当x=6,y=-1时,原式=-2;(4)原式=(2-2b)x2+(a+3)x-6y+5,∵代数式的值与字母x的取值无关,∴2-2b=0且a+3=0,∴a=-3,b=1,∴ab=(-3)...

x³+2a(x²+xy)-bx²-xy+y² =x³+(2a-b)x²+(2a-1)xy+y² x³、y²系数均不等于0,此两项恒存在,又得到的是三次二项式,因此化简后,(2a-b)x²、(2a-1)xy两项不存在,系数=0 2a-b=0 2a-1=0 解得a=1/2...

令x-1=s,y+2=t,即x=1+s ,y=t-2,代入得 f(x,y)=4(1+s)^2+(1+s)(t-2)-(t-2)^2-6(1+s)-3(t-2)+5打开化简得 =4s^2-t^2+st+2t+3=3+2t+4s^2+st-t^2。 f(x,y)=e^xln(1+y)=(1+x+x^2/2+x^3/3+....)(y-y^2/2+y^3/3+....) =y+xy-y^2...

(1)原式=3x2+9,当x=-2时,原式=12+9=21;(2)原式=3x2y-2xy2+2xy-3x2y-xy+3xy2=xy2+xy,当x=3,y=-13时,原式=13-1=-23.

(1)原式=3x2y-(6xy-8xy+4-x2y)+1=3x2y-6xy+8xy-4+x2y+1=4x2y+2xy-3,当x=-12时,原式=y-y-3=-3.(2)设原式中的被减数为A,根据题意得:A+(xy-2yz+3zx)=2yz-3zx+2xy,则A=(2yz-3zx+2xy)-(xy-2yz+3zx)=2yz-3zx+2xy-xy+2yz-3zx=4yz-6zx...

(1)-2x -4xy-y ;(2)5x +11xy+2y ;(3)2x +4xy+y 试题分析:先根据题意分别列出代数式,再去括号、合并同类项即可. (1)B-A=(-3xy-x )-(x +xy+y )=-3xy-x -x -xy-y =-2x -4xy-y ;(2)2A-3B=2(x +xy+y )...

(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.

证明:如果有整数x,y使方程成立, 则 由17*29-5 = 488 = 4x^2+12xy-8y^2 = (2x+3y)^2-17y^2 知(2x+3y)^2+5能被17整除. 设2x+3y=17n+a,其中a是0,±1,±2,±3,±4,±5,±6,±7,±8中的某个数,但是这时 (2x+3y)^2+5 =(17n)^2+34na+(a^2+5...

若(x-2)的平方+|y-1|=0, 则x-2=0 x=2 y-1=0 y=1 4xy-(2x的平方+5xy-y的平方)+2(x的平方+3xy) =4xy-2x²-5xy+y²+2x²+6xy =5xy+y² =5×2×1+1 =11

解: 1、 算术平方根有意义,1-2x≥0,2x-1≥0 2x-1=0 x=½ y=√(1-2x)+√(2x-1)+√(x²-2x+1) =0+0+√(x-1)² =|x-1| =|½-1| =½ (x+y)²⁰¹⁰-xy=(½+½)²⁰¹⁰-½·½...

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