A<B

Thấy nó to hơn

Học tốt nha

Có \(P=\frac{1}{2}\times\frac{3}{4}\times\frac{5}{6}\times...\times\frac{399}{400}< \frac{2}{3}\times\frac{4}{5}\times...\times\frac{400}{401}\)

=> \(P^2< \frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{400}{401}=\frac{1}{401}< \frac{1}{400}=\frac{1}{20}\)

=> \(P< \frac{1}{20}\)(đpcm).

chuẩn

1300 : [120 - (x - 9)] = 25

=> 120 - x + 9 = 52

=> x = 77.

x + (9 – 14) = 29 + (-39)

=> x + 9 - 14 = -10

=> x = -5

(-16) + |x| = (-12) + (-21)

=> |x| = -12 - 21 + 16

=> |x| = -17 (vô lý)

=> \(x\in\varnothing\)

a) \(\frac{0,75-0,6+\frac{3}{7}+\frac{3}{11}}{2,75-2,2+\frac{11}{7}+\frac{11}{13}}=\frac{\frac{3}{4}-\frac{3}{5}+\frac{3}{7}+\frac{3}{13}}{\frac{11}{4}-\frac{11}{5}+\frac{11}{7}+\frac{11}{13}}=\frac{3\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{13}\right)}{11\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{13}\right)}=\frac{3}{11}\)

b) \(\frac{x+1}{2018}+\frac{x+2}{2017}+\frac{x+3}{2016}+\frac{x+4}{2015}=-4\)

<=> \(\frac{x+1}{2018}+1+\frac{x+2}{2017}+1+\frac{x+3}{2016}+1+\frac{x+4}{2015}+1=0\)

<=> \(\left(x+2019\right)\left(\frac{1}{2018}+\frac{1}{2017}+\frac{1}{2016}+\frac{1}{2015}\right)=0\)

<=> \(x+2019=0\)(Vì 1/2018 + 1/2017 + 1/2016 + 1/2015 khác 0)

<=> x = -2019

Tính S = 1302 - 335 + 72.

a. S = 1302 - 335 + 72 = (1302 - 72) + 335 = 1569.

b. S = 1302 - (335 + 72) = 1302 - 407 = 895.

c. S = (1302 - 335) + 72 = 1039.

B = 15 . 513 - 1024 = 7695 - 1024 = 6671 là đúng . Vì đối trường hợp k có ngoặc thì nhân chia trc cộng trừ sau nên A sẽ bị sai vì trừ trc vậy còn lại B là đúng

Hok tốt

\(B=\frac{1}{1.4}+\frac{2}{4.10}+\frac{3}{10.19}+\frac{4}{19.31}\)

\(3B=\frac{3}{1.4}+\frac{6}{4.10}+\frac{9}{10.19}+\frac{12}{19.31}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{10}+\frac{1}{10}-\frac{1}{19}+\frac{1}{19}-\frac{1}{31}\)

\(=1-\frac{1}{31}=\frac{31}{31}-\frac{1}{31}=\frac{30}{31}\)

\(\Rightarrow B=\frac{30}{31}\div3=\frac{10}{31}\)

Vậy \(B=\frac{10}{31}\).

       B = 1/1.4 + 2/4.10 + 3/10.19 + 4/19.31

=> 3B = 3/1.4 + 6/4.10 + 9/10.19 + 12/19.31

=> 3B = 1 - 1/4 + 1/4 - 1/10 + 1/10 - 1/19 + 1/19 - 1/31

=> 3B = 1 - 1/31 

=> 3B = 30/31

=> B  = 30/31 : 3

=> B = 10/31

Vậy B = 10/31

Trl :

x = 0

HokT~

Tui cx là Army nè :33

a2021

b2023

A. 1997 + 24 = (1997 + 3) + (24 - 3)

                      = 2000 + 21

                      = 2021

B. 29 + 1994 = (29 - 6) + (1994 + 6)

                     =  23 + 2000

                     = 2023