1999⼀（1999+1999⼀2000）+1⼀2000等于多少？

应该是1999/（1999+1999/2000）+1/2001
=1999/[1999×(1+1/2000)]+1/2001
=1/(1+1/2000)+1/2001
=2000/2001+1/2001
=1

解：=1999*2000/（1999*2001）+）+1/2000
=2000/2001+1/2000
=1-1/2001+1/2000
=1+1/（2000*2001）
=4002001/4002000
望楼主采纳！！！！

1999/（1999+1999/2000）+1/2000
=1999/[1999(1+1/2000)]+1/2000
=1/(2001/2000)+1/2000
=2000/2001+1/2000
=(2000*2000+2001)/2001*2000
=4002001/4002000

1999/(1999+1999/2000)+1/2000
=1999/[1999*(2000+1)/2000]+1/2000
=1999*2000/1999*2001+1/2000
=2000/2001+1/2000
=(2000*2000+2000+1）/（2000*2001）
={【2000*（2000+1）】+1}/(2000*2001)
=1+1/(2000*2001)

1999/(1999+1999/2000)+1/2001
=1999/{[1999*2000+1999]/2000}+1/2001
=1999*2000/（1999*2000+1999*1）+1/2001
=1999*[2000/1999*（2000+1）]+//2001
=1999*[2000/1999*2001]+1/2001
=2000/2001+1/2001
=1