goi tu so la x
vi tu so nho hon mau so 6 don vi => mau so =x+6
vay phan so ban dau la x/x+6
neu them 17 don vi...............2 don vi => p/s moi = x+17/x+8
thi dc 1 phan so bang nghich dao cua phan so ban dau X+17/x+8=x+6/x
=> x(x+17)=(x+8)(x+6)
     x^2+17x=x^2+14x+48
      17x-14x=x^2-x^2+48
       3x=48
=>x=16
=> phan so ban dau la 16/22
minh giai cho ban roi do nhơ like cho minh nha