19991999 . 1998 - 19981998.1999

= 1999 . 1001 . 1998 - 1998 . 1001 . 1999

= 0

tick nhé bạn

19991999 . 1998 - 19981998.1999

= 1999 . 1001 . 1998 - 1998 . 1001 . 1999

= 0

a) Ta có: \(1990.1990-1992.1998=1990.1990-\left(1990+2\right).\left(1990-2\right)\)

                                                                     \(=1990.1990-1990.1990+4\)

                                                                     \(=4\)

b) Ta có: \(\left(2+4+6+...+100\right).\left(36.333-108.111\right)\)

        \(=\left(2+4+6+...+100\right).\left(36.3.111-36.3.111\right)\)

        \(=\left(2+4+6+...+100\right).0\)

        \(=0\)

c) Ta có: \(19991999.1998-19981998.1999\)

        \(=10001.1999.1998-10001.1998.1999\)

        \(=0\)

=-19916

    1990 x 1990 - 1992 x 1998

= (1992 - 2)x1990 - 1992 x (1990 - 2)

= 1992 x 1990 - 2 x 1990 - 1992 x 1990 + 1992 x 2

= 1992 x 2 - 2 x 1990

= (1992 - 1990) x 2

=       2   x 2 

= 4

mot manh dat hcn dai 48 m. chieu rong bang 3/4 chieu dai nguoi ta trong rau cu 4m thu duoc 10 kg  rau

tinh dien tinh thu duoc 10 kg rau

tinh so kg rau thu duoc

a) ( 1+ 2+3+4+......+100) . ( 1 + 4 + 9 +.....+100) : ( 65 . 111 -13 .15 .37 )

= ( 1+ 2+3+4+......+100) . ( 1 + 4 + 9 +.....+100) : ( 13.5 . 3.37 - 13.15.37)

= ( 1+ 2+3+4+......+100) . ( 1 + 4 + 9 +.....+100) : ( 13.15.37 - 13.15.37)

= ( 1+ 2+3+4+......+100) . ( 1 + 4 + 9 +.....+100) : 0

Sai đề r bn ơi :((

b) 19991999 . 1998 - 19981998 . 1999

= ( 19981998 + 10001) .1998 - 19981998 . ( 1998+1)

= 19981998 .1998 + 10001 .1998 - 19981998 .1998 + 19981998

= 0

úng đề rồi 

1990 . 1990 - 1992 . 1998

=3 960 100-3 980 016

=-19 916

1998*1990+3978/1992*1991-3988=3976008,003

4011799.02661

Mik sửa lại đề

\(\frac{1989.1990+3978}{1992\cdot1991-3984}\)

Trả lời

\(\frac{1989.1990+3978}{1992.1991-3984}\)

\(=\frac{1989.1990+1989\cdot2}{1992.1991-1992.2}\)

\(=\frac{1989.\left(1992-2\right)}{1992\left(1991-2\right)}\)

\(=\frac{1989.1990}{1992.1989}\)

\(=\frac{1990}{1992}\)

\(=\frac{995}{996}\)