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化简:(1)2(2a-3b)+3(2b-3a)(2)2(x2-xy)...

解:(1)原式=3a-2b+5a-7b-4a+8b =3a+5a-4a-2b-7b+8b=4a-b; (2)原式= - = + + -2 ;(3)原式=-x 2 +2xy-y 2 -2xy+6x 2 +6y-3xy=-x 2 +6x 2 +2xy-2xy-3xy-y 2 +6y 2 =5x 2 -3xy+5y 2 。

(1)原式=2x2y-2xy2+3x2y2-3x2y2-3x2y2+3xy2=2x2y+xy2-6x2y2,当x=-1,y=2时,原式=4-4-24=-24;(2)原式=12a2b-4ab2+5ab2-5a2b-2a2b-12=5a2b+ab2-12,∵(15-a)2+|b-5|=0,∴a=15,b=5,则原式=1+5-12=-6.

(1)原式=4x2-2xy-x2+xy+6,=3x2-xy+6.(2)原式=b+a2-2(a2-2a2+b),=b+a2-2a2+4a2-2b,=3a2-b.

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...

根号下大于等于0 所以x-2≥0且4-2x≥0 x≥2且x≤2 同时满足则x=2 y=0-0+1=1 所以原式=[1/(x+y)+2/x(x-y)]÷(x+2)/2x =[x(x-y)+2(x+y)]/x(x+y)(x-y)÷(x+2)/2x =(x²-xy+2x+2y)/x(x+y)(x-y)×2x/(x+2) =2(x²-xy+2x+2y)/(x+y)(x-y)(x+2) =2(4-2+...

(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 )...

x^3+2a(x^2+xy)-bx^2-xy+y^2 =x^3+(2a-b)x^2(2a-1)xy+y^2 2a-b=0,2a-1=0 a=1/2,b=1 a^3+b^2 =1/8+1 =9/8

3b-2a=0 a-3=0 2a-3b-2c=0 得出a=3 b=2 c=0 -(a+b+c)-[(b+2a-c)-2b]=-5-(2+6-4)= -9

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=-4a?ab2+(-4a)?3a2b+(-4a)?(-1)=-4a2b2-12a3b+4a.(2)原式=34x6y2÷(-0.6xy)+65x3y5÷(-0.6xy)+(-0.9x2y3)÷(-0.6xy)=-54x5y-2x2y4+32xy2.(3)原式=a3-2a2+3a-6-a3+2a2+2a=5a-6.(4)原式=4x2-4xy+y2-4x2-8xy+4xy+8y2...

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