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a,
= 51 - 2022 + 2022
= 51
b, = -2019 - 11 + 2019
= -11
c, = 27 - 52 - 37 + 52
= -10
d, = 19 - 32 + 41 - 19 + 25 - 41
= -7
sách Nâng cao phát triển lớp 6 tập 1
(3965-2378)-(437-1378)-528
=3965-2378-437-1378-528
=(3965-(437+528))-(2378-1378)
=3000-1000
=2000
Bài 1 :
\((3965-2378)-(437-1378)-528\)
\(=3965-2378-437+1378-528\)
\(=3965-(2378-1378)-(437+528)\)
\(=3965-1000-965\)
\(=(3965-965)-1000\)
\(=3000-1000\)
\(=2000\)
Bài 2 :
\((-x+31)-39=-69+11\)
\((-x+31)-39=-58\)
\(-x+31=-58+39\)
\(-x+31=-19\)
\(-x=-19-31\)
\(-x=-50\)
\(=>x=50\)
A = \(\dfrac{2020}{2021}\) + \(\dfrac{2021}{2022}\) ; B = \(\dfrac{2020+2021}{2021+2022}\)
B = \(\dfrac{2020+2021}{2021+2022}\) = \(\dfrac{2020}{2021+2022}\) + \(\dfrac{2021}{2021+2022}\)
\(\dfrac{2020}{2021}\) > \(\dfrac{2020}{2021+2022}\)
\(\dfrac{2021}{2022}\) > \(\dfrac{2021}{2021+2022}\)
Cộng vế với vế ta có:
A = \(\dfrac{2020}{2021}\) + \(\dfrac{2021}{2022}\) > \(\dfrac{2020}{2021+2022}\) + \(\dfrac{2021}{2021+2022}\) = B
Vậy A > B
A = \(\dfrac{10^{10}-1}{10^{11}-1}\)
A \(\times\) 10 = \(\dfrac{(10^{10}-1)\times10}{10^{11}-1}\) = \(\dfrac{10^{11}-10}{10^{11}-1}\) = 1 - \(\dfrac{9}{10^{11}-1}\) < 1
B = \(\dfrac{10^{10}+1}{10^{11}+1}\)
B \(\times\) 10 = \(\dfrac{(10^{10}+1)\times10}{10^{11}+1}\) = \(\dfrac{10^{11}+10}{10^{11}+1}\) = 1 + \(\dfrac{9}{10^{11}+1}\) > 1
Vì 10 A< 1< 10B
Vậy A < B
a) -370 b)22