giup minh voi may ban oi 

a: =-3/4+1/2-1/13+3/13=-1/4+2/13=-13/52+8/52=-5/52

b: =10/11+1/11-1/8=1-1/8=7/8

c: =4(2,86+3,14)-30,05+9x0,75

=24-30,05+6,75

=0,7

a: \(=\dfrac{1}{3}+\dfrac{1}{8}-\dfrac{3}{16}\cdot4=\dfrac{11}{24}-\dfrac{3}{64}=\dfrac{88}{192}-\dfrac{9}{192}=\dfrac{79}{192}\)

b: \(=\dfrac{5}{8}\cdot\left(-16\right)=-10\)

c: \(=\left(\dfrac{8}{5}+\dfrac{1}{3}\right):\dfrac{29}{5}-\dfrac{4}{81}\cdot9\)

\(=\dfrac{29}{15}\cdot\dfrac{5}{29}-\dfrac{4}{9}=\dfrac{1}{3}-\dfrac{4}{9}=-\dfrac{1}{9}\)

\(c,=4\cdot\left(-\dfrac{1}{8}\right)-2\cdot\dfrac{1}{4}-\dfrac{3}{2}+1=-\dfrac{1}{2}-\dfrac{1}{2}-\dfrac{3}{2}+1=-\dfrac{3}{2}\\ \left(5x+\dfrac{2}{3}\right)^2=\dfrac{1}{4}\Rightarrow\left[{}\begin{matrix}5x+\dfrac{2}{3}=\dfrac{1}{2}\\5x+\dfrac{2}{3}=-\dfrac{1}{2}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}5x=-\dfrac{1}{6}\\5x=-\dfrac{7}{6}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-\dfrac{1}{30}\\x=-\dfrac{7}{30}\end{matrix}\right.\\ c,x:2=\left(-4\right):5\Rightarrow x=-\dfrac{4}{5}\cdot2=-\dfrac{8}{5}\)

1 >

2 <

3 <

B7 chu vi mảnh vườn là 3,3 m

diện tích là \(\dfrac{8}{7}\)m vuông

Bài 7:

Chu vi là:

\(\left(\dfrac{12}{5}+\dfrac{10}{21}\right)\cdot2=\dfrac{604}{105}\left(m\right)\)

Diện tích là:

\(\dfrac{12}{5}\cdot\dfrac{10}{21}=\dfrac{8}{7}\left(m^2\right)\)

B8 chu vi hình thoi là 20,8 m

diện tich hinh thoi là 22,8 m vuông 

tick cho mk

dễ mà bạn

a)3x-18=0                     à mà mik chx hc phương trình 

3x=18+0                          sorry bạn nhé

3x=18

x=18:3

x=6

vậy x=6

a)\(3x-18=0\)

\(\Leftrightarrow3x=18\)

\(\Leftrightarrow x=6\)

Vậy x=6

b)\(2x.\left(x-4\right)-3x+12=0\)

\(\Leftrightarrow2x.\left(x-4\right)-3\left(x-4\right)=0\)

\(\Leftrightarrow\left(2x-3\right).\left(x-4\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-3=0\\x-4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{3}{2}\\x=4\end{cases}}}\)

Vậy .......

c)\(\frac{x-1}{2}-\frac{x+3}{3}=x+1\)

\(\Leftrightarrow6.\left(\frac{x-1}{2}-\frac{x+3}{3}\right)=6.\left(x+1\right)\)

\(\Leftrightarrow3.\left(x-1\right)-2.\left(x+3\right)=6x+6\)

\(\Leftrightarrow3x-3-2x-6=6x+6\)

\(\Leftrightarrow3x-2x-6x=6+3+6\)

\(\Leftrightarrow-5x=15\)

\(\Leftrightarrow x=-3\)

Vậy x= -3

d)\(\frac{x-3}{x+3}-\frac{5}{3-x}=\frac{30}{x^2-9}\)

\(\Leftrightarrow\frac{x-3}{x+3}-\frac{-5}{x-3}=\frac{30}{\left(x+3\right).\left(x-3\right)}\)

\(\Leftrightarrow\frac{\left(x-3\right).\left(x-3\right)}{\left(x+3\right).\left(x-3\right)}-\frac{-5.\left(x+3\right)}{\left(x-3\right).\left(x+3\right)}=\frac{30}{\left(x-3\right).\left(x+3\right)}\)

\(\Leftrightarrow\left(x-3\right)^2-\left(-5\right).\left(x+3\right)=30\)

\(\Leftrightarrow x^2-6x+9-\left(-5x-15\right)=30\)

\(\Leftrightarrow x^2-6x+9+5x+15-30=0\)

\(\Leftrightarrow x^2-x-6=0\)

\(\Leftrightarrow x^2-3x+2x-6=0\)

\(\Leftrightarrow x.\left(x-3\right)+2.\left(x-3\right)=0\)

\(\Leftrightarrow\left(x+2\right).\left(x-3\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x+2=0\\x-3=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=-2\\x=3\end{cases}}}\)

Vậy......

Câu d)

ĐKXĐ:\(x\ne\pm3\)

Cái x=3 loại

Lấy cái x=-2

?????

giúp j hả bn

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

- 1999 . 19981998 + 19991999 . 1998

= - 1999 . 1998 . 10001 + 1999 . 10001 . 1998

= 10001 . 1998 ( - 1999 + 1999 )

= 10001 . 1998 . 0

= 0

-1999.19981998+19991999.1998=0

hok tốt

=-1998(19981998-19991999)

=-1998.-1

=1998

kb vs **** cho mik nha