急,几道分式计算题分子和分母的最高次项的数为正数 -x²-2x-1/5+4x-3x²已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值已知x+1/x=3,求分式x²+1/x²的值
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![急,几道分式计算题分子和分母的最高次项的数为正数 -x²-2x-1/5+4x-3x²已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值已知x+1/x=3,求分式x²+1/x²的值](/uploads/image/z/698634-18-4.jpg?t=%E6%80%A5%2C%E5%87%A0%E9%81%93%E5%88%86%E5%BC%8F%E8%AE%A1%E7%AE%97%E9%A2%98%E5%88%86%E5%AD%90%E5%92%8C%E5%88%86%E6%AF%8D%E7%9A%84%E6%9C%80%E9%AB%98%E6%AC%A1%E9%A1%B9%E7%9A%84%E6%95%B0%E4%B8%BA%E6%AD%A3%E6%95%B0+-x%26sup2%3B-2x-1%2F5%2B4x-3x%26sup2%3B%E5%B7%B2%E7%9F%A51%2Fx-1%2Fy%3D5%2C%E6%B1%82%E5%88%86%E5%BC%8F3x%2B5xy-3y%2Fx-3xy-y%E7%9A%84%E5%80%BC%E5%B7%B2%E7%9F%A5x%2B1%2Fx%3D3%2C%E6%B1%82%E5%88%86%E5%BC%8Fx%26sup2%3B%2B1%2Fx%26sup2%3B%E7%9A%84%E5%80%BC)
急,几道分式计算题分子和分母的最高次项的数为正数 -x²-2x-1/5+4x-3x²已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值已知x+1/x=3,求分式x²+1/x²的值
急,几道分式计算题
分子和分母的最高次项的数为正数 -x²-2x-1/5+4x-3x²
已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值
已知x+1/x=3,求分式x²+1/x²的值
急,几道分式计算题分子和分母的最高次项的数为正数 -x²-2x-1/5+4x-3x²已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值已知x+1/x=3,求分式x²+1/x²的值
1/x-1/y=5
1/y-1/x=-5
(3x+5xy-3y)/(x-3xy-y)(分子分母同时除以xy)
=(3x/xy+5xy/xy-3y/xy)/(x/xy-3xy/xy-y/xy)
=(3/y+5-3/x)/(1/y-3-1/x)
=(3/y-3/x+5)/(1/y-1/x-3)
=(-5*3+5)/(-5-3)
=-10/(-8)
=5/4
x²+1/x²
=(x+1/x)²-2
=3²-2
=9-2
=7
(1)(-x^2-2x-1)/(5+4x-3x^2)=(x^2+2x+1)/(3x^2-4x-5)
(2)因为:1/x-1/y=5,得到:y-x=5xy
所以:(3x+5xy-3y)/(x-3xy-y)=[3(x-y)+5xy]/[(x-y)-3xy]
=(-15xy+5xy)/(-8xy)=5/4
(3)x^2+1/x^2=(x+1/x)^2-2=9-2=7