1990 x 1990 - 1992 × 1988

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

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

= 1990 × 1988 + 1990 × 2 - 1990 × 1988 - 2 × 1988

= 1990 × 2 - 2 × 1988

= 2 × (1990 - 1988)

= 2 × 2

= 4

Ủng hộ mk nha ^_-

1990.1990-1992.1998

=(1992-2).(1988+2)-(1992.1988)

=2.2

=4

Mk thấy 2 bạn kia hình như bạn nào cũng đúng thì phải!
NHƯNG MK SẼ THÍCH BẠN NÀO LÀM GỌN NHANH HƠN!

     \(1990\times1990-1992\times1988\)

 \(=\left(1988+2\right)\times1990-\left(1990+2\right)\times1988\)

  \(=1988\times1990+2\times1990-1990\times1988-2\times1988\)

  \(=2\times1990-2\times1988\)

  \(=2\times\left(1990-1988\right)\)

  \(=2\times2\)

   \(=4\)

=4

C = 1988 . 1990 + 2 - 1990 - 1990 - 1988 - 2 . 1988

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

C = 2 . ( 1990 - 1988 ) + 0

C = 2 + 2 + 0

C = 4

1990x1990-1992x1988

=4:))

free fire

liên quân

yamatecuraxai

a) 1990.1990 - 1992.1988

= 1990.1990 - (1990 + 2)(1990 - 2)

= 1990.1990 - 1990.1990 + 4 = 4

b) (1374.57 + 687.86) : (870 + 235.122)

= (1374.57 + 687.2.43) : (10.87 + 5.47.2.61)

= (1374.57 + 1374.43) : (10.87 + 10.47.61)

= [1374(57 + 43)] : [10(87 + 47.61)]

= (1374.100) : [10(87 + 47.61)] (đoạn này mẫu số xấu quá, hetcuu)

c) (124.237 + 152) : (870 + 235.122)

= (124.235 + 124.2 + 152) : (870 + 235.122)

= (122.235 + 2.235 + 2.124 + 152) : (870 + 235.122)

= (122.235 + 470 + 248 + 152) : (235.122 + 870)

= (122.235 + 870) : (235.122 + 870) = 1

d) \(\dfrac{423134\cdot846267-423133}{846267\cdot423133+423134}=\dfrac{423133\cdot846267+846267-423133}{846267\cdot423133+423134}\)

\(=\dfrac{423133\cdot846267+423134}{846267\cdot423133+423134}=1\)

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)1990.1990+1992.1988

=3960100+3960096

=7920196

b)(124.237+152):(870+235.122)

=(29388+152):(870+28670)

=29540:29540

=1

c)(423134.846267-423133):(846267.423133+423134)

=(423134.846267):(423133-423134)

=(423134.846267):0

=0