\(\frac{5+55+555+5555}{9+99+999+9999}=\frac{5\cdot\left(1+11+111+1111\right)}{9\cdot\left(1+11+111+1111\right)}=\frac{5}{9}\)
\(\frac{5+55+555+5555}{9+99+999+9999}\)
= \(\frac{5.\left(1+11+111+1111\right)}{9.\left(1+11+111+1111\right)}\)
= \(\frac{5}{9}\)
rut gon phan so : 5+55+555+5555