(8.) 5/x=4/3x1 5/x=4/3 4x=5×3=15 x=15/4 即三又四分之三兆手. (9) x+3/4=x/5 x-x/闹族5=-3/4 (4/5)x=-3/4 x=(-3/4)÷(4/5) =(-3/4)×(5/4) =-15/16. (10) 10x=1/x+2 10x^2=1+2x 10x^2-2x-1=0 解得 x=1±√11 (11) 5x+1/5=x/2 5x-x/2=-1/5 (9/2)/x=-1/5 x=(-1/5)÷(9/2) =-(1/5×(2/9) =-2/45. (12) 8+5/4=x/3 x/3=8+5/4 =(8×4)/4+5/4 =32/4+5/4 =37/4. x=3*37/4 =101/4 即二十五又四分之一. (13) x+2/液猜弊4=3x-2/5 3x-x=2/4+2/5 =1/2+2/5 =5/10+4/10 =9/10 2x=9/10 x=(9/10)÷2 =(9/10)×1/2 =9/20. (14) 3x+2/4-3=5 3x+1/2-3=5 3x+1/2-6/2=5 3x-5/2=5 3x=5+5/2 =10/2+5/2 =15/2 x=(15/2)÷3 =(15/2)×(1/3) =15/6 =5/2. 即二又二分之一. (15) 2x-1/3+4=1/2 2x-1/3+12/3=1/2 2x+11/3=1/2 2x=1/2-11/3 =3/6-22/6 =-19/6 x=(-19/6)÷2 =(-19/6)×(1/2) =-19/12. 即负一又一十二分之七 (17) 3x+1/4-3/2=5 3x+1/4-6/4=5 3x-5/4=5 3x=5+5/4 =25/4 x=(25/4)÷3 =(25/4)×(1/3) =25/12 即二又一十二分之一 (18) 2x+7/5+1/3=-4 2x+21/15+5/15=-4 2x+26/15=-4 2x=-4-26/15 =-60/15-26/15 =-86/15 x=-(86/15)÷2 =-(86/15)×1/2 =-43/15. 即负三又一十五分之一十三. (19) 3x+1/2-5=1/4 3x+1/2-10/2=1/4 3x-9/2=1/4 3x=1/4+9/2 =1/4+18/4 =19/4 x=(19/4)÷3 =(19/4)×(1/3) =19/12. 即一又一十二分之七. (20) x+3/5+3/2=-2 x+6/10+15/10=-2 x+21/10=-2 x=-2-21/10 =-20/10-21/10 =-41/10. 即负四又十分之一.
标签：19x,俄罗斯
