若3x-2y-z=0,x+4y-3z=0,求3x²+y²/4x²-y²+z²的值_数学解答

若3x-2y-z=0,x+4y-3z=0,求3x²+y²/4x²-y²+z²的值

人气：208 ℃　时间：2020-06-06 13:15:45

解答

(1)3x-2y-z=0,(2)x+4y-3z=0,(1)×2+(2)得7x-5z=0∴x=5z/7把x=5z/7代入(1)得15z/7-2y-z=0∴y=4z/7把x=5z/7,y=4z/7代入原式得原式=(25z²/49+16z²/49)/(100z²/49-16z²/49+z²)=41/133...