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先化简再求值:设:A=2x^2-3xy+y^2-x+2y B=4x^2-6x...

麻烦你看下你的题 有些地方是不是有括号 你没加

∵|x-3a|≥0,(y+5)^2≥0 又:|x-3a|+(y+5)^2=0 ∴|x-3a|=(y+5)^2=0 ∴x=3a,y=-5 a=B-2A= 4x^2-6xy+2y^2-3x-y -2(2x^2-3xy+y^2-x+2y ) = 4x^2-6xy+2y^2-3x-y -4x^2+6xy-2y^2+2x-4y = -x-5y x=3a=-3x-15y x=-15y/2=-15*(-5)/2=75/2 A = 2x^2-3xy+y^2-...

分解因式是吧: a(x-y)^3+b(y-x)^2 =a(x-y)^3+b(x-y)^2 =(x-y)^2·(ax-ay)+(x-y)^2·b =(x-y)^2·(ax-ay+b) 4x^3-6x^2-2x =2x(2x^2-3x-1) 有理数范围内只能到这里了

把你的QQ给我~我做完传图给你O(∩_∩)O~~

|x+2a|+(y+3)^2=0 x=-2a,y=-3 B-2A=a a=4x^2-6xy+2y^2-3x-y-2(2x^2-3xy+y^2-x+2y) =4x^2-6xy+2y^2-3x-y-4x^2+6xy-2y^2+2x-4y =-x-5y |x-2a| =|x-2(-x-5y)| =|x+2x+10y| =|3x+10y| =|3x-30| =0 解得x=10 A=2x^2-3xy+y^2-x+2y =(x-y)(2x-y)-x+2y ...

(1)原式=-a2+12a-2-12a+2=-a2,把a=-12代入得:原式=-14; (2)∵A=x2-3x-6,B=2x2-4x+6,∴3A-2B=3(x2-3x-6)-2(2x2-4x+6)=3x2-9x-18-4x2+8x-12=-x2-x-30,当x=1时,原式=-1-1-30=-32.

A=2x^2-3xy+2y^2,B=2x^2+xy-3y^2 求①A+B ②A-(B-2A) ①A+B =2x^2-3xy+2y^2+2x^2+xy-3y^2 =4x^2-2xy-y^2 ②A-(B-2A) =A-B+2A =3A-B =3(2x^2-3xy+2y^2)-(2x^2+xy-3y^2 ) =6x^2-9xy+6y^2-2x^2-xy+3y^2 =4x^2-10xy+9y^2

由已知得:y=6-2x,代入u=4x 2 +3xy+y 2 -6x-3y,整理得:u=2x 2 -6x+18,而x≥0,y=6-2x≥0,则0≤x≤3,u=2(x- 3 2 ) 2 + 27 2 ,当x=0或x=3时,u取得最大值,u max =18,当x= 3 2 时,u取得最小值,u min = 27 2 .故选A.

解:y^2=4x y=2x+b,得 4x^2+(4b-4)x+b^2=0 设点A和点B的坐标分别为(x1,y1),(x2,y2)(其中y10) 则,x1+x2=-(b-1),x1x2=b^2/4 同理可求得,y^2-2y+2b 则y1+y2=2, y1y2=2b 因为弦长AB=3根号5,而|AB|=根号【(y2-y1)^2+(x2-x1)^2】 而(y2-y1)^2=...

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