椭圆3x^2+4y^2=12x^2/4+y^2/3=1a^2=4,b^2=3,c=1右准线x=4,A(-2,0)B（2，0）设P(4,m)m≠0PA:y=m/6(x+2),PB:y=m/2(x-2）y=m/6(x+2)与3x^2+4y^2=12联立消去y得：(m^2+27)x^2+4m^2x+4m^2-108=0 M(x1,y1),则-2x1=(4m^2-108)/(m^2+27)
x1=(54-2m^2)/(m^2+27)
y1=m/6(x1+2)=18m/(m^2+27) y=m/2(x-2)与3x^2+4y^2=12联立消去y得 (m^2+3)x^2-4m^x+4m... |
