có tất cả số số là:

(678-2):2+1=339(số)

tổng trên là:

(2+678)x339:2=115260

chúc bạn học giỏi

130515

130515

B=4+8+12+...+96-8-16-24-...-96

B=4

\(B=...\)

\(=\left(4+12+20+...+92\right)+\left(8+16+24+...+96\right)-\left(8+16+...+96\right)\)

\(=4+12+20+...+92\)

\(=\left(4+92\right)\times\left[\frac{\left(92-4\right)}{8}+1\right]=96\times12=1152\)

B = ( 4 + 8 + 12 + ... + 96 ) - ( 8 + 16 + 24 + ... + 96 )

B = 4 + 12 + 20 + 18 + ... + 92

Số số hạng của dãy số B là : 

( 92 - 4 ) : 8 + 1 = 12 (số hạng)

Tổng của dãy số B là :

( 92 + 4 ) x 12 : 2 = 576

=))

calculator

calculator dùng đi

khong dung duoc nha ban 

ban biet thi tra loi dum

khong thi dung nhan linh tinh

\(a,x-7\frac{5}{8}=1\frac{1}{4}\)

=> \(x-\frac{61}{8}=\frac{5}{4}\)

=> \(x=\frac{5}{4}+\frac{61}{8}\)

=> \(x=\frac{10}{8}+\frac{61}{8}=\frac{71}{8}=8\frac{7}{8}\)

\(b,x+7\frac{5}{8}=9\frac{1}{4}\)

=> \(x+\frac{43}{5}=\frac{37}{4}\)

=> \(x=\frac{37}{4}-\frac{43}{5}=\frac{13}{20}\)

\(c,\left[x-7\frac{5}{8}\right]:\frac{1}{2}=3\)

=> \(\left[x-\frac{61}{8}\right]=3\cdot\frac{1}{2}\)

=> \(\left[x-\frac{61}{8}\right]=\frac{3}{2}\)

=> \(x-\frac{61}{8}=\frac{3}{2}\)

=> \(x=\frac{3}{2}+\frac{61}{8}=\frac{12}{8}+\frac{61}{8}=\frac{73}{8}=9\frac{1}{8}\)

d, \(\frac{x}{1\cdot3}+\frac{x}{3\cdot5}+\frac{x}{5\cdot7}+...+\frac{x}{97\cdot99}=99\)

=> \(\frac{x}{2}\left[\frac{2}{1\cdot3}+\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+...+\frac{2}{97\cdot99}\right]=99\)

=> \(\frac{x}{2}\left[1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\right]=99\)

=> \(\frac{x}{2}\left[1-\frac{1}{99}\right]=99\)

=> \(\frac{x}{2}\cdot\frac{98}{99}=99\)

=> \(\frac{98x}{198}=99\)

=>  98x = 99 . 198

=> 98x = 19602

=> x = 19602 : 98 = 9801/49

a) \(x-7\frac{5}{8}=1\frac{1}{4}\)

=> \(x=\frac{5}{4}+\frac{61}{8}\)

=> \(x=\frac{71}{8}\)

b) \(x+7\frac{5}{8}=9\frac{1}{4}\)

=> \(x=\frac{37}{4}-\frac{61}{8}\)

=> \(x=\frac{13}{8}\)

c) \(\left(x-7\frac{5}{8}\right):\frac{1}{2}=3\)

=> \(x-\frac{61}{8}=3.\frac{1}{2}\)

=> \(x-\frac{61}{8}=\frac{3}{2}\)

=> \(x=\frac{3}{2}+\frac{61}{8}\)

=> \(x=\frac{73}{8}\)

d) \(\frac{x}{1.3}+\frac{x}{3.5}+...+\frac{x}{97.99}=99\)

=> \(x.\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{97.99}\right)=99\)

=> \(\frac{1}{2}x\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{97}-\frac{1}{99}\right)=99\)

=> \(x\left(1-\frac{1}{99}\right)=99:\frac{1}{2}\)

=> \(x.\frac{98}{99}=198\)

=> \(x=198:\frac{98}{99}=\frac{9801}{49}\)

\(b,\text{ }x+7\frac{5}{8}=9\frac{1}{4}\)

\(x=9\frac{1}{4}-\left(7+\frac{5}{8}\right)\)

\(x=9+\frac{1}{4}-7-\frac{5}{8}\)

\(x=\left(9-7\right)+\left(\frac{1}{4}-\frac{5}{8}\right)\)

\(x=2+-\frac{3}{8}\)

\(x=2\frac{-3}{8}\)

4 has not been - broke

5 did you - was

6 have youy ever been

II

1 go

2 were

3 eats

7 does - won't worry

8 had played - would have won

9 will - do

10 were - would go

14 would have written

15 won't go

16 tries

17 spoke

19 finish - will go

20 see - ask

Rewrite

1 The man who doesn't work hard can't earn more money

3 If my friend and I had enough money, we would buy a  house of our town

4 If the weather were better now, we could go for a walk

5 If I knew his addres, I would give it to you

6 If he worked slowly enough, he wouldn't make

7 If I were sent to proson, she would visit me 

8 If I won a big prize in a lottery, I would give up my job

9 If the doctor weren't so late, he could see many patients

10 If tickets weren't expensive, we would visit them in Ha Noi

III

1 were

2 would visit

3 would give

Dang 4 day ạ

Cố tình trồng cây

Cây hoa ko lên

Vô tình hít thở

Vậy mak tăng cân ....

hết ak

Bạn!

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~ Hok tốt ~

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Cho con hi vọng

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