dkfr.net
当前位置:首页 >> 2x 3y 2 28x 2y 4xy >>

2x 3y 2 28x 2y 4xy

-2x³y²+28x²y-4xy =-2xy(x²y-14x+2)

x^2-4xy+3y^2-4x+10y+3 =(x-y)(x-3y)-4x+10y+3 =(x-y-3)(x-3y-1) x^2+xy-2y^2+2x+7y-3 =(x-y)(x+2y)+2x+7y-3 =(x-y+3)(x+2y-1)

解: (2x+y)²-(2x+3y)(2x-3y)-2(x-2y)² =(4x²+4xy+y²)-(4x²-9y²)-2(x²-4xy+4y²) =4x²+4xy+y²-4x²+9y²-2x²+8xy-8y² =-2x²+12xy+2y²

1/x - 1/y = 2 x-y = -2xy 2x-2y - 5xy = -9xy 3x-3y+4xy = -2xy 值=2/9

4x3y-8x2y2+4xy3=4xy(x2-2xy+y2)=4xy(x-y)2.故选D.

设y'=p 则代入原方程得 p³-4xyp+8y²=0 ==>x=p²/4y+2y/p.(1) 令f(y,p)=p²/4y+2y/p ∵f'y=-p²/(4y²)+2/p f'p=p/(2y)-2y/p² ∴代入公式 (1-f'y*p)dy-f'p*pdp=0 得 [1+(p²/(4y²)-2/p)p]dy-[p/(2y)-2y/p&...

(1)原式=-2x-4x+2y+3x-2y+1=-3x+1,当x=-3时,原式=10;(2)原式=xy-2y2-8xy+6y2-2x2y+30y2-4x2y=-7xy+34y2-6x2y,当x=1,y=-2时,原式=162.

因为|x-a|和(y+4)方都是大于等于0的。要想|x-a|+(y+4)方=0成立只有|x-a|=0和(y+4)方=0,所以可以知道x=a,y=-4; A-2B=6x+3=3a;结合x=a可以求得x的值为-1 然后A的值就可以求出来了..

x2+4xy+4y2x?3y÷x2?4y23x?6y+x3y?x=(x+2y)2x?3y?3(x?2y)(x+2y)(x?2y)-xx?3y=3(x+2y)x?3y-xx?3y=2x+6yx?3y,∵x:y=3:5且x≠0.∴设x=3k,y=5k,原式=6k+30k3k?15k=-3.

网站首页 | 网站地图
All rights reserved Powered by www.dkfr.net
copyright ©right 2010-2021。
内容来自网络,如有侵犯请联系客服。zhit325@qq.com