x,y满足x2+2xy+3y2=2,x+2y的范围
人气:340 ℃ 时间:2019-12-14 22:41:16
解答
最傻的办法是令t=x+2y
所以x=t-2y带回第一式
(t-2y)^2+2(t-2y)y+3y^2=2
3y^2-2ty+(t^2-2)=0
为了使之有解必须有
Δ=4t^2-12(t^2-2)>=0
8t^2
推荐
- 尽量快些,x,y是非0的实数,且X2+2xy-3y2=0,求—2Y/X=多少
- x-2y-1=0,x2-2xy-3y2=0
- 已知x2-2xy=3y2且x,y为非零实数 求:(1)2x+y/x-2y (2)2x2-3y2+5xy/x2+xy+y2
- 已知x2-2xy-3y2=0求(2x+3y)/2y
- 若x/y=2,求x2-2xy-3y2/x2-6xy-7y2的值
- 1 Daniel dose his homework every evening.改为否定句 2 Her English teacher lives in Spring Street
- 已知y=f(x)是偶函数,当x>0时,f(X)=x+a/x(a>0),当x大于等于-3小于等于-1时,n≤f(x)≤m恒成立.
- 现在分词做状语,如果主句的谓语动词是过去式,那状语不是用过去完成时吗
猜你喜欢