x1+x2+x3=y1+y2+y3=x1y1+x2y2+x3y3=0,求x1^2/(x1^2+x2^2+x3^2)+y1^2/(y1^2+y2^2+y3^2)的取值范围

已知A(x1,y1),B(x2,y2),C(x3,y3),求二次函数的a b c找到了a=(y3)/(((x2)-(x3))*((x1)-(x3)))+(y2)/(((x2)-(x3))*((x2)-(x1)))+(y1)/(((x1)-(x2))*((x1)-(x3)));b=((y2)-(y1)-a*((x2)*(x2)-(x1) *(x1)))/((x2)-(x1));c=y1-a*(x1)*(x1)-b*x1; matlab如何将一组数代入原方程的字母里?syms x1 x2 x3 x4 y1 y2 y3 y4 X1 X2 X3 X4 Y1 Y2 Y3 Y4A=[x1,y1,1,0,0,0,-x1*X1,-y1*X1;0,0,0,x1,y1,1,-x1*Y1,-y1*Y1;x2,y2,1,0,0,0,...-x2*X2,-y2*X2;0,0,0,x2,y2,1,-x2*Y2,-y2*Y2;x3,y3,1,0,0,0,-x3*X3,-y3*X3; MATLAB 已知3点求夹角>> x1=1;y1=1;x2=0;y2=0;x3=0;y3=3;theta=acosd(dot([x1-x2,y1-y2],[x3-x2,y3-y2])/(norm([x1-x2,y1-y2])*norm([x1-x2,y3-y2])))theta =47.8696>> x1=1;y1=1;x2=0;y2=0;x3=0;y3=3;theta=acos(dot([x1-x2,y1-y2],[x3-x2,y3-y2])/(norm([x1-x2, 点(x1,y1),(x2,y2),(x3,y3)其中x1 若x1/y1 =x2/y2 =x3/y3 =1/2,则（x1+x2-x3)/（y1+y2-y3）=? 在反比例y=-1/x的图像中,有三点（x1,y1),(x2,y2),(x3.y3),若x1>x2>0>x3,y1,y2,y3,的关系 证明：√[（x1-x2)^2+(y1-y2)^2]+√[(x2-x3)^2+(y2-y3)^2]>=√[(x1-x3)^2+(y1-y3)^2],x,y均为实数. 设向量组x1,x2,x3,x4线性相关,y1=x1+x2,y2=x2+x3,y3=x3+x1,讨论向量组的线性关系. 关于一原二次函数的三点式就是加入抛物线过3个点(x1,y1).(x2,y2).(x3,y3)则他的解析式就是f(x)=((x-x2)(x-x3)/(x1-x2)(x1-x3))*y1+((x-x1)(x-x2)/(x2-x1)(x2-x3))y2+((x-x3)(x-x1)/(x3-x1)(x3-x2))y3应该怎么来证明一下不管 已知A(x1,y1)、B(x2,y2)、C(x3,y3)是函数y= 已知变量x1,x2,x3,由变量y1,y2,y3线性表示为：X1=2Y1+2Y2+Y3 X2=3Y1+Y2+5Y3 X3=3Y1+2Y2+3Y3试将变量Y1,Y2,Y3由变量X1,X2,X3表示 已知线性变换X1=2Y1+2Y2+Y3,X2=3Y1+Y2+5Y3,X3=3Y1+2Y2+3Y3,（三个式子用大括号括起）求从变量X1,X2,X3到变 x1+x2+x3=y1+y2+y3=x1y1+x2y2+x3y3=0,求x1^2/(x1^2+x2^2+x3^2)+y1^2/(y1^2+y2^2+y3^2)的取值范围 在函数y=5/x图像上有三点A1(x1,y1)A2(x2,y2)A3(x3,y3)已知x1 lingo线性规划请问这个模型对吗?是线性规划吗?我是个菜鸟MaxGDP=0.6734X1+0.2536X2+0.4733X3;0.1315X1+0.0260X2+0.0069X3+Y1=X1；0.1774X1+0.6231X2+0.2322X3+Y2=X2；0.0177X1+0.0973X2+0.2876X3+Y3=X3；Y1/X1>=0.3346;Y2/X2>=0.1555;Y3/X3>= 两条垂直的直线,一条经过(x1,y1) (x2,y2),另一条经过(x3,y3) (x4,y4),求交点的坐标.我手头上已经有一种算法和我自己的不一样,我没能看懂a=(x2-x1)*(y3-y1)-(y2-y1)*(x3-x1)/(y2-y1)*(x4-x3)-(x2-x1)*(y4-y3)x=x3+a*(x4-x 十万火急~已知：x1＜x2＜x3,y1＜y2＜y3 x1+x2+x3=y1+y2+y3 x1x2+x2x3+x3x1=y1y2+y2y3+y3已知：x1＜x2＜x3,y1＜y2＜y3x1+x2+x3=y1+y2+y3x1x2+x2x3+x3x1=y1y2+y2y3+y3y1若x1＜y1求证；x2＞y2且x3小于y3我一点思路也没有,麻烦把过 关于一个简单的线性变换已知X1=2y1+2y2+y3x2=3y1+y2+5y3x3=3y1+2y2+3y3求x1 x2 x3 到y1 y2 y3 的线性变换需解答过程