已知3x-2y-5z=0,2x-5y+4z=0,且x.y.z均不为0,求3x^2+2y^2+5z^2/5x^2+y^2-9z^2的_数学解答

已知3x-2y-5z=0,2x-5y+4z=0,且x.y.z均不为0,求3x^2+2y^2+5z^2/5x^2+y^2-9z^2的值

人气：415 ℃　时间：2019-10-09 13:55:23

解答

3x-2y-5z=0 12x-8y-20z=02x-5y+4z=0 10x-25y+20z=0两式相加22x-33y=022x=33yy=2/3x3x-2y-5z=0 15x-10y-25z=02x-5y+4z=0 4x-10y+8z=0两式相减11x-33z=011x=33zz=1/3x3x^2+2y^2+5z^2/5x^2+y^2-9z^2=(3x^2+8/9x^2+5/9x^...