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a) A =123 . 137137
A = 123 . ( 137 . 1001 )
A = ( 123 . 137 ) . 1001
B = 137 . 123123
B = 137 . ( 123 . 1001 )
B = ( 137 . 123 ) . 1001
=> A = B
b) C = 199 . 201
C = 199 . ( 200 + 1 )
C = 199 . 200 + 199 . 1
D = ( 199 + 1 ) . 200
D = 199 . 200 + 1 . 200
Có 199 . 200 = 199 . 200. Mà 199 . 1 < 200 . 1
=> C < D
a, Ta có :
A = 123 . 137137
A = 123 . ( 137 . 101 )
A = 137 . 101 . 123
B = 137 . 123123
B = 137 . ( 123 . 101 )
B = 123 . 101 . 137
=> A = B
b, Ta có :
C = 199 . 201
C = 199 . ( 200 + 1 )
C = 199 . 200 + 199 . 1
D = 200 . 200
D = ( 199 + 1 ) . 200
D = 199 . 200 + 1 . 200
=> C < D
Ta co:
A = 199 x (200 + 1)
= 199 x 1 + 199 x 200 = 199 x 200 + 199
B = 200 x (199 + 1)
= 200 x 199 + 200 x 1 = 200 x 199 + 200
Vi 199 x 200 + 199 < 200 x 199 + 200
Nen A < B
a) Ta có: A = 123 x 123 = 123 x ( 124 - 1 ) = 123 x 124 - 123
B = 121 x 124 = ( 123 - 2 ) x 124 = 123 x 124 - 248
Suy ra: 123 x 124 - 123 > 123 x 124 - 248 hay A > B
b) Ta có: C = 123 x 137137 = 123 x 137 x 1001 = 137 x 123 x 1001
D = 137 x 123123 = 137 x 123 x 1001
Suy ra: C = D
c) Ta có: E = 2015 x 2017 = 2015 x ( 2016 + 1 ) = 2015 x 2016 + 2015
F = 2016 x 2016 = ( 2015 + 1 ) x 2016 = 2015 x 2016 + 2016
Suy ra: 2015 x 2016 + 2015 < 2015 x 2016 + 2016 hay E < F
A=201.199=(200+1).199=200.199+199
B=200.200=(199+1).200=199.200+200
Vì 200.199+199<199.200+200 nên A<B
\(\frac{199}{200}>\frac{199}{200+201+202}\)
\(\frac{200}{201}>\frac{200}{200+201+202}\)
\(\frac{201}{202}>\frac{201}{200+201+202}\)
=>\(A>B\)
Do \(\frac{199}{200}\)> \(\frac{199}{200+201+202}\), \(\frac{200}{201}\)>\(\frac{200}{200+201+202}\),\(\frac{201}{202}\)>\(\frac{201}{200+201+202}\)nên A>B
a) A = 199 x 201
= 199 x 200 + 199
B = 200 x 200
= 200 x 199 + 200
A = 199 x 200 +199 va B = 199 x 200 + 200
=> A < B
b) Có 35 x 53 < 53 x 54 ; -18 < 35
=> C < D
c) E = 1998 x 1998
E = 1998 x 2000 - 1998 x 2
F = 1996 x 2000
F = 1998 x 2000 - 2 x 2000
ma 1998 x 2 < 2 x 2000
=> 1998 x2000 - 1998 x 2 > 1998 x 2000 - 2 x 2000
=> E < F
a > A < B
b> C < D
c> E > F
k mk nha học tốt
\(A=\frac{199}{200}+\frac{200}{201}+\frac{201}{202}< \frac{199}{200+201+202}+\frac{200}{200+201+202}+\frac{201}{200+201+202}\)
A \(< \frac{199+200+201}{200+201+202}=B\)
\(A< B\)
Ta có: \(A=\frac{199}{200}+\frac{200}{201}+\frac{201}{202}< \frac{199}{200+201+202}+\frac{200}{200+201+202}+\frac{201}{200+201+202}< \)
\(< \frac{199+200+201}{200+201+202}\)
Vậy A < B
ỦNG HỘ TỚ NHA
Ta có : A = 199.201 = (200 - 1)(200 + 1) = 2002 - 1
Mà : B = 2002
Nên : A < B
