\(1998\cdot502+1999\cdot498\)

\(=1998\cdot502+1998\cdot498+1\cdot498\)

\(=1998\cdot\left(502+498\right)+498\)

\(=1998\cdot1000+498\)

\(=1998000+498\)

\(=1998498\)

Chúc bạn học tốt!!!

số cần tìm là:1998x502+1999x498=1998498

                                    k mình nha

chúc bạn hok tốt

1998x502+1999x498

=1002996+995502

=1998498

NHO K CHO MINH NHE NEU CO BAI KHO TO NHAC CHO

KET BAN VOI MINH NHE 

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

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

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

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

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

\(=0\)

1999 x 2011 - 1999

=1999 x 2011 -1999 x 1

=1999x(2011-1)

=1999 x 2010

= 4017990

  2010 x 1998 - 2010 

=2010 x 1998 -2010 x 1

= 2010 x ( 1998 -1 )

= 2010 x  1997 

= 4013970

a)1999 x 2011 - 1999

= 4019989 - 1999

= 4017990

b)2010 x 1998 - 2010

= 4015980 - 2010

= 4013970

Mong bạn k mik

Là 1 e nhé!!!
1998 x 2000 - 1414 : 1999 x 1998 + 584
= (2000 - 1999) x (1414 +584) : 1998
=         1          x      1998      :  1998
=              1998                     : 1998
=                           1
Do lâu r cj chưa lm nên nếu có j thì e kiểm tra lại nhé <3

(1999×1998+1998+1997)×(1/1+1/2:3/2-4/3)

(1999×1998+1998+1997)×(1/1+1/2×2/3-4/3)

1999×1998+1998+1997)×(1/1+1/3-4/3)

(1999×1998+1998+1997)×(4/3-4/3)

(1999×1998+1998+1997)×0

0

bằng 0 nha bn

giai cho tao nhanh ko con bao

Sửa lại :

\(=\frac{1999.2000+1999-1}{1998+1999.2000}.\frac{7}{5}=\frac{1999.2000+1998}{1998+1999.2000}.\frac{7}{5}=1.\frac{7}{5}=\frac{7}{5}\)

\(\frac{1999.2000-1}{1998+1999.2000}.\frac{7}{5}\)

= \(\frac{-1}{1998}\) . \(\frac{7}{5}\)

= \(\frac{-7}{9990}\)

\(\frac{1999.2000+1999}{1998+1999.2000}.\frac{7}{5}=1+\frac{1}{1998+1999.2000}.\frac{7}{5}=1+\frac{7}{5.\left(1998+1999.2000\right)}=1+\frac{7}{19999990}=\frac{19999997}{19999990}\)