若实数x,y,z满足3x+7y+z=1,4x+10y+z=2005,求分式x+3y/2004x+2004y+2004z的值.
问题描述:
若实数x,y,z满足3x+7y+z=1,4x+10y+z=2005,求分式x+3y/2004x+2004y+2004z的值.
答
用4x+10y+z=2005减去3x+7y+z=1得x+3y=2004用3x+7y+z=1乘以3得9x+21y+3z=3-----P用4x+10y+z=2005乘以2得8x+20y+2z=4010-----Q用方程p减去方程q得x+y+z=-4007所以所求式子为2004/2004*-4007=-1/4007...