Em tham khảo:
$\frac{x-1}{8}+$$\frac{x-1}{9}=$$\frac{x-1}{10}+$$\frac{x-1}{11}$
⇔ $\frac{x-1}{8}+$$\frac{x-1}{9}-$$\frac{x-1}{10}-$$\frac{x-1}{11}=0$
⇔$(x-1)$.($\frac{1}{8}+$$\frac{1}{9}-$$\frac{1}{10}-$$\frac{1}{11}$) $=0$
Vì $\frac{1}{8}+$$\frac{1}{9}-$$\frac{1}{10}-$$\frac{1}{11}>0$
⇔$x-1=0$
⇔$x=1$
HỌC TỐT
@Chin...........