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2 tháng 9 2021

a,19.21=(20-1)(20+1)=202-12=400-1=399

29.31=(30-1)(30+1)=302-12=900-1=899

39.41=(40-1)(40+1)=402-12=1600-1=1599

6 tháng 5 2017

a) 135 + x -135 = 0 => (135 - 135) + x = 0 => x = 0.

b) -562 - x + 562 = 0 => (-562 + 562) - x = 0 => - x = 0 => x = 0.

c) 61 + x - 23 = 91=> (61 - 23) + x = 91=>38 + x = 91=> x = 53.

d) 11 + 53 - x = 97 => 64 - x = 97 => x = 64 - 97 => x = - 33

10 tháng 12 2019

\(M=\dfrac{6}{10.13}+\dfrac{6}{13.16}+\dfrac{6}{16.19}+\dfrac{6}{19.21}\)

\(\dfrac{1}{2}M=\dfrac{3}{10.13}+\dfrac{3}{13.16}+\dfrac{3}{16.19}+\dfrac{3}{19.21}\)

\(\dfrac{1}{6}M=\dfrac{1}{10}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{21}\)

\(\dfrac{1}{6}M=\dfrac{1}{10}-\dfrac{1}{21}\)

\(M=\dfrac{11}{210}:\dfrac{1}{6}=\dfrac{11}{35}\)

\(N=\dfrac{1}{20}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{26}+\dfrac{1}{26}-\dfrac{1}{29}+\dfrac{1}{29}-\dfrac{1}{30}\)

\(=\dfrac{1}{20}-\dfrac{1}{30}\)

\(=\dfrac{1}{60}\)

 

\(\dfrac{M}{N}=\dfrac{11}{35}:\dfrac{1}{60}=\dfrac{132}{7}\)\(\dfrac{132}{25}\)

14 tháng 10 2021

mong các bn giúp mình gấp ạ ^^

a: =>x-562=20

=>x=582

b: =>562-x+568=0

=>1130-x=0

=>x=1130

c: =>2x-123=283-62=221

=>2x=344

=>x=172

d: =>2x-1=2

=>2x=3

=>x=3/2

26 tháng 2 2022

\(A=7\left(\dfrac{1}{10}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{12}+...+\dfrac{1}{69}-\dfrac{1}{70}\right)\)

\(=7\left(\dfrac{1}{10}-\dfrac{1}{70}\right)=\dfrac{7.60}{700}=\dfrac{420}{700}=\dfrac{3}{5}\)

\(B=\dfrac{1}{2}\left(\dfrac{1}{25}-\dfrac{1}{27}+\dfrac{1}{27}-\dfrac{1}{29}+...+\dfrac{1}{73}-\dfrac{1}{75}\right)\)

\(=\dfrac{1}{2}\left(\dfrac{1}{25}-\dfrac{1}{75}\right)=\dfrac{1}{75}\)

29 tháng 12 2022

789. 2- 56+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

= 1578- 56+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1522+ (-95)+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1427+111+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1538+261+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1799+498-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2297-215+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2082+49+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2131+1236-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=3367-4591-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=-1224-56+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=-1280+4189+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2909+48+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2957+52-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=3009-1000-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=2009-500+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1509+230+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=1739+32500-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=34239-5600+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=28639+2641+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=31280+853+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=32133+195-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=32328-564+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=31764+235+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=31999+4187+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=36186+9023177-5000000+562+159-90+459-420+562+235+489+71+12

=9059363-5000000+562+159-90+459-420+562+235+489+71+12

=4059363+562+159-90+459-420+562+235+489+71+12

=4059925+159-90+459-420+562+235+489+71+12

=4060084-90+459-420+562+235+489+71+12

=4059994+459-420+562+235+489+71+12 

=4060453-420+562+235+489+71+12 

=4060033+562+235+489+71+12 

=4060595+235+489+71+12

=4060830+489+71+12

=4061319+71+12=4061402

29 tháng 12 2022

ủa:q. rảnh v:))

6 tháng 11 2016

bạn vào đây xem câu trả lời

https://www.youtube.com/watch?v=fvGaHwKrbUc

6 tháng 11 2016

562=2x281

446=2x223

123=3x41

ƯCLN(562;446;123)=1