a, 1990 x 1990 - 1992 x 1998

= 1990 x 1990 - ( 1992 - 2 ) x ( 1998 + 2 )

= 1990 x 1990 - 1990 x 2000

= 1990 x ( 2000 - 1990 )

= 1990 x 10

= 19900

a) 1990 x 1990 - 1992 x 1998

=1990 x 1998 - 1992

= 1990 x 6

= 11940

1990 x 1990 - 1992 x 1998

= 1990 x 1990 - ( 1992 - 2 ) x ( 1998 + 2 )

= 1990 x 1990 - 1990 x 2000

= 1990 x ( 2000 - 1990 )

= 1990 x 10

= 19900

b.\(\frac{1374.57+1374.34}{26.13+74.13+74}=\frac{1374.91}{1374}=91\)

a, 1990 . 1990 - 1982 . 1998

= ( 1982 + 8 ) . 1990 - 1982 . ( 1990 + 8 )

= 1982 .1990 + 8 .1990 - ( 1982 . 1990 + 8 . 1982 )

= 1982 . 1990 + 8 .1990 - 1982 . 1990 - 8 . 1982

= ( 1982 .1990 - 1982 . 1990 ) + ( 8 . 1990 - 8 . 1982 )

=  8 . ( 1990 - 1982 )

=               8 . 8

=                64

Mình sửa đề bài chút xíu nha 1992 thành 1982 

 a) 
1990.1990 -1992.1998 = (1995-5)^2 -(1995+3)(1995-3) = -10.1995 +25 +9 = -(19950-34) = -19916 
b) 
ta có
tu = 124 .237 +152 = 122.137 + 474 +152= 122. 137 + 626 
mau = ( 870 + (237-2).122= 870 +122.237 - 244 =122.237 + 626 
=> phân thức đã cho = tử/mẫu = 1

a/ \(=1990.1990-\left(1990+2\right).\left(1990-2\right)=1990.1990-\left(1990.1990-4\right)=4\)

b/ \(=\frac{2.687.57+687.86}{26.13+74.\left(13+1\right)}=\frac{687\left(2.57+86\right)}{26.13+74.13+74}=\frac{687.\left(114+86\right)}{13\left(26+74\right)+74}=\)

\(=\frac{687.200}{13.100+74}=\frac{687.200}{1374}=\frac{687.200}{687.2}=\frac{200}{2}=100\)

c/ \(=\frac{214.237+152}{870+\left(237-2\right).\left(124-2\right)}=\frac{124.237+152}{870+124.237-2.237-2.124+4}=\)

\(=\frac{124.237+152}{124.237+870+4-2.237-2.124}=\frac{124.237+152}{124.237+152}=1\)

cảm ơn nha Nguyễn Ngọc Anh Minh!

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

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