1998 x 497 + 1998 x1 + 1998 x1 + 1998 x1

= 1998 x (497 +1 + 1 + 1 )

=1998 x 500 

= 999000

1998 x 497 + 1998 + 1998 + 1998

= 1998 x 497 + 1998 x 3

= 1998 x ( 497 + 3 )

= 1998 x 500

= 999000

1998 x 497 + 1998 + 1998 + 1998

= 1998 x 497 + 1998 x 3

= 1998 x ( 497 + 3 )

= 1998 x 500

= 999000

1998^2-1997(1998+1)

=1998^2-(1998-1)(1998+1)

=1998^2-(1998^2-1)

=1998^2-1998^2+1

=1

=1998.1998-1996.(1998+2)

=1998.1998-1996.1998+1996.2

=1998.(1998-1996)+1996.2

=1998.2+1996.2

=2.(1998+1996)

=2.3994

=7988

1998.1998-1996.2000=4

1998x1998-1996x2000=(1996+2)x1998-1996x(1998+2)=1996x1998+2x1998-1996x1998+1996x2=2x1998-1998x2=2x(1998-1996)=2x2=4

Tick nhé Tạ_Thu_Hiền

câu thứ nhất bằng 7876638900

câu thứ 2 bằng 798081399759

1990.1990-1992.1988

=1990.(1988+2)-(1990+2).1988

=1990.1988+1990.2-1990.1988+1988.2

= (1990-1988).2

=2.2

=4

\(=\left(1999\times1998+1998\times1997\right)\times\left(1+\dfrac{1}{2}:1\dfrac{1}{2}-1\dfrac{1}{3}\right)\)

\(=\left(1999\times1998+1998\times1997\right)\times\left(1+\dfrac{1}{2}:\dfrac{3}{2}-\dfrac{4}{3}\right)\)

\(=\left(1999\times1998+1998\times1997\right)\times\left(1+\dfrac{1}{3}-\dfrac{4}{3}\right)\)

\(=\left(1999\times1998+1998\times1997\right)\times\left(\dfrac{4}{3}-\dfrac{4}{3}\right)\)

\(=\left(1999\times1998+1998\times1997\right)\times0\)

\(=0\)

\(\frac{1998.2000-1020}{1999.1998+978}=\frac{1998.\left(1999+1\right)-1020}{1999.1998+978}=\frac{1998.1999+978}{1999.1998+978}=1\)

1) (1998.1999 - 1998.1998 - 1900 - 98) : 2016

= [1998.(1999 - 1) - 1998) : 2016

= (1998 - 1998) : 2016

= 0 : 2016

= 0

2) 2015.2015 - 2013.2017

= 2015² - (2015 - 2).(2015 + 2)

= 2015² - (2015² - 2²)

= 2015² - 2015² + 4

= 4

\(\dfrac{\text{1998 x 10001 x 1999}}{\text{1998 x 10001 x 1999}}=1\)