解方程组: 5x^2+2y^2+x-4y-6=0 2x^+y^2+x-2y-3=0

显示全部楼层 · 2012-7-13 19:57:03

5x2+2y2+x-4y-6=0 ①2x2+y2+x-2y-3=0②将②×2，得：4x2+2y2+2x-4y-6=0③将①－③，得：x2-x=0
x（x-1)=0∴x?=0,x?=1将x?=0代入②，得：y?=3,y?=-1将x?=1代入②，得：y?=0,y?=2∴x?=0，y?=3x?=0，y?=-1x?=1，y?=0x&#8...

千问 · 2012-7-13 19:57:03

2x^2+y^2+x-2y-3=04x^2+2y^2+2x-4y-6=0 与1式相减 x^2-x=0x(x-1)=0x1=0x2=1 x=0时2y^2-4y-6=0y^2-2y-3=0(y-3)(y+1)=0y1=3y2=-1 x=1时5+2y^2+1-4y-6=02y^2-4y=0...

千问 · 2012-7-13 19:57:03

5x^2+2y^2+x-4y-6=0① 2x^2+y^2+x-2y-3=0②①-②×2，得x2-x=0x=1或x=0 代入①则x=0 y=3，x=0 y=-1，x=1 y=0，x=1 y=2...

千问 · 2012-7-13 19:57:03

第二式乘2，相减x^2-x=0x(x-1)=0x1=0…x2=1当x=0时y^2-2y-3=0(y-3)(y+1)=0y1=3…y=-1当x=1时y^2-2y=0y1=0…y2=2...

千问 · 2012-7-13 19:57:03

左式减右式的2倍即好，后面很简单...