Question

 

Chứng minh rằng 

\(\dfrac{5}{13.18}=\dfrac{1}{13}-\dfrac{1}{8}\)

Answer 1

\(\dfrac{1}{13}-\dfrac{1}{18}=\dfrac{18}{13.18}-\dfrac{13}{13.18}=\dfrac{18-13}{13.18}=\dfrac{5}{13.18}\)

Answer 2

\(\dfrac{5}{13\cdot18}=\dfrac{18}{13\cdot18}-\dfrac{13}{13\cdot18}=\dfrac{1}{13}-\dfrac{1}{18}\)(đpcm)