X²/4+Y²/9=1y=2xx^2/4+4x^2/9=1 25x^2/36=1x1=6/5 y1=12/5x2=-6/5 y2=-12/5则X1X2+Y1Y2=-36/25-144/25=-36/5请参考……
把y=2x带入椭圆x2/4+y2/9=1x2/4+4x2/9=1求的x2=11/36y2=4x2所以x2+y2=5*11/36=55/36
