解方程组:X+Y+Z=6.5 X/4+Y/4+Z/5=96/60 Z/3+Y/4+X/5=108/60

1个回答

  • 由X+Y+Z=6.5得x+y+z=13/2 ①

    X/4+Y/4+Z/5=96/60 ②

    Z/3+Y/4+X/5=108/60 ③

    ①去分母乘2得2x+2y+2z=13 ④

    ②去分母乘60得15x+15y+12z=96 ⑤

    ③去分母乘60得20z+15y+12x=108 ⑥

    由④乘15得30x+30y+30z=195 ⑦

    由⑤乘2得30x+30y+24z=192 ⑧

    ⑦-⑧:6z=3 z=1/2

    ⑤-⑥:3x-8z=-12 ⑨

    把z=1/2代入⑨得3x-4=-12 x=-8/3

    把z=1/2,x=-3/8代入①得-8/3+y+1/2=13/2

    得y=26/3

    所以x=-8/3,y=26/3,z=1/2