Question

\(\dfrac{1999x2001-1}{1998+1999x2000}\)x\(\dfrac{7}{5}\)
Mọi người giúp mk với 

Answer 1

     \(\dfrac{1999\times2001-1}{1998+1999\times2000}\) \(\times\) \(\dfrac{7}{5}\)

= \(\dfrac{1999\times\left(2000+1\right)-1}{1998+1999\times2000}\) \(\times\) \(\dfrac{7}{5}\)

= \(\dfrac{1999\times2000+1999-1}{1998+1999\times2000}\) \(\times\) \(\dfrac{7}{5}\)

= \(\dfrac{1999\times2000+1998}{1999\times2000+1998}\) \(\times\) \(\dfrac{7}{5}\)

= 1 \(\times\) \(\dfrac{7}{5}\)

= \(\dfrac{7}{5}\)