2道数学题快的加分！！！

显示全部楼层 · 2009-3-14 09:53:46

1.已知线段x、y满足(x*x+9y*y):xy=6:1,求2x-3y/3x+2y的值。（要过程）
2.已知a,b,c为△ABC的三边，且(a-c):(a+b):(b-c)=-2:7:-1,试判断△ABC的形状。（要过程）

千问 · 2009-3-14 09:53:46

1 x^2+9y^2=6xy x^2+9y^2-6xy=0 (x-3y)^2=0 x=3y (2x-3y)/(3x+2y)=(6y-3y)/(9y+2y)=3/113 7(a-c)=-2(a+b) 化简得9a-7c+2b=07(b-c)=-(a+b)化简得a+8b-7c=0由这两个方程可得 8a-6b=0 a=3b/4 7c=(3/4)b+8b=35b/4c=(5/4）b故a^2+b^2=(25/4)b^2=c^2三角形为直角三角形...

千问 · 2009-3-14 09:53:46

1 (x*x+9y*y):xy=6:1
x*x +9y*y - 6xy = 0;(x-3y)^2 = 0;x = 3y;2x-3y/3x+2y = 3y/11y = 3/112 (a-c):(a+b):(b-c)=-2:7:-1 设 a-c = -2k; a+b = 7k;b-c = -k则:a=...

千问 · 2009-3-14 09:53:46

1 (x*x+9y*y):xy=6:1 x*x +9y*y - 6xy = 0; (x-3y)^2 = 0; x = 3y; 2x-3y/3x+2y = 3y/11y = 3/11 2 (a-c):(a+b):(b-c)=-2:7:-1 设 a-c = -2k; a+b = 7k; b-c = -k 则: ...

2道数学题 快的加分！！！

2道数学题快的加分！！！