已知x/3=y/1+z/2,求(2x²-2y²+5z²)/(xy+yz+xz)的值
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/27 19:08:05
![已知x/3=y/1+z/2,求(2x²-2y²+5z²)/(xy+yz+xz)的值](/uploads/image/z/4333189-13-9.jpg?t=%E5%B7%B2%E7%9F%A5x%2F3%3Dy%2F1%2Bz%2F2%2C%E6%B1%82%EF%BC%882x%26%23178%3B-2y%26%23178%3B%2B5z%26%23178%3B%EF%BC%89%2F%EF%BC%88xy%2Byz%2Bxz%EF%BC%89%E7%9A%84%E5%80%BC)
已知x/3=y/1+z/2,求(2x²-2y²+5z²)/(xy+yz+xz)的值
已知x/3=y/1+z/2,求(2x²-2y²+5z²)/(xy+yz+xz)的值
已知x/3=y/1+z/2,求(2x²-2y²+5z²)/(xy+yz+xz)的值
设3/x=1/y/=2/z=k,则,x=3/k,y=1/k,z=2/k
代人,得,
(2x²-2y²+5z²)/(xy+yz+xz)
=(18/k²-2/k²+20/k²)/(3/k²+2/k²+6/k²)
=(36/k²)/(11/k²)
=36/11
设x/3=2,y/1=z/2=1,则 x=6,y=1,z=2,带入右边=(2*36-2*1+5*4)/(6*1+1*2+2*6)
=(72-2+20)/(6+2+12)=90/20=4.5