2:

a: =4+3/8+5+2/3

=9+3/8+2/3

=216/24+9/24+16/24

=216/24+25/24

=241/24

b; =2+3/8+1+1/4+3+6/7

=6+3/8+1/4+6/7

=6+5/8+6/7

=419/56

c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)

=6+3/8-1/4+1/3

=6+1/8+1/3

=6+11/24

=155/24

d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)

=3+13+5/6

=16+5/6

=101/6

e: =3+1/2+4+5/7-5-5/14

=3+4-5+1/2+5/7-5/14

=2+7/14+10/14-5/14

=2+12/14

=2+6/7=20/7

f: =9/2+1/2:11/2

=9/2+1/11

=99/22+2/22=101/22

2:

a: =4+3/8+5+2/3

=9+3/8+2/3

=216/24+9/24+16/24

=216/24+25/24

=241/24

b; =2+3/8+1+1/4+3+6/7

=6+3/8+1/4+6/7

=6+5/8+6/7

=419/56

c: \(=2+\dfrac{3}{8}-1-\dfrac{1}{4}+5+\dfrac{1}{3}\)

=6+3/8-1/4+1/3

=6+1/8+1/3

=6+11/24

=155/24

d: \(=3+\dfrac{5}{6}+6\cdot\dfrac{13}{6}\)

=3+13+5/6

=16+5/6

=101/6

e: =3+1/2+4+5/7-5-5/14

=3+4-5+1/2+5/7-5/14

=2+7/14+10/14-5/14

=2+12/14

=2+6/7=20/7

f: =9/2+1/2:11/2

=9/2+1/11

=99/22+2/22=101/22

a)3/5xX=4/7

=>X=4/7:3/5

=>X=20/21

b)1/8:X=1/5

=>X=1/8:1/5

=>X=5/8

a, x=4/7:3/5

x=4/7x5/3

x=20/21

b,x=1/8:1/5

x=1/8x5/1

x=5/8

câu 1: -10

câu 2: -50

\(a.\dfrac{4}{5}+x=\dfrac{8}{10}\\ \Rightarrow x=\dfrac{8}{10}-\dfrac{4}{5}\\ \Rightarrow x=\dfrac{8}{10}-\dfrac{8}{10}\\ \Rightarrow x=0\\ b.\dfrac{1}{7}-7\left(\dfrac{2}{3}-x\right)=-\dfrac{4}{7}\\ \Rightarrow\dfrac{1}{7}-\dfrac{14}{3}+7x=-\dfrac{4}{7}\\ \Rightarrow-\dfrac{95}{21}+7x=-\dfrac{4}{7}\\\Rightarrow7x=\dfrac{83}{21}\\ \Rightarrow x=\dfrac{83}{147} \)

`a)4/5+x=8/10`

`=>x=8/10-4/5`

`=>x=4/5-4/5`

`=>x=0`

Vậy `x=0`

__

`b)1/7-7(2/3-x)=-4/7`

`=>7(2/3-x)=1/7-(-4/7)`

`=>7(2/3-x)=1/7+4/7`

`=>7(2/3-x)=5/7`

`=>2/3-x=5/7:7`

`=>2/3-x=5/7xx1/7`

`=>2/3-x=5/49`

`=>x=2/3-5/49`

`=>x=98/147-15/147`

`=>x=83/147`

Vậy `x=83/147`

a. =[(-4)(-25)].3=100.3=300

b. =[(-8).125][5.2]=-1000.10=-10000

c. =[25.(-4)][(-5).20]=-100(-100)=10000

bủh

b1

A,=\(\frac{35}{54}\)   B,=4

b2

A,x=\(\frac{7}{15}\)  B=\(\frac{-9}{7}\) 

CHÚC BẠN HỌC GIỎI

a)\(\left(x+3\right)\times5+1=20\Leftrightarrow5x+15=19\)

\(\Leftrightarrow5x=4\Leftrightarrow x=\frac{4}{5}\)

b)sai đề

c)\(2\frac{3}{7}\times x+1\frac{5}{4}=5\frac{3}{42}\)\(\Leftrightarrow\frac{17}{7}\times x+\frac{9}{4}=\frac{71}{14}\) \(\Leftrightarrow\frac{17}{7}\times x+\frac{63}{28}=\frac{142}{28}\)

\(\Leftrightarrow\frac{17}{7}\times x=\frac{79}{28}\Leftrightarrow x=\frac{17}{7}:\frac{79}{28}\) \(\Leftrightarrow x=\frac{17}{7}\times\frac{28}{79}\Leftrightarrow x=\frac{476}{553}=\frac{68}{79}\)

d)\(10\frac{2}{3}-x:\frac{6}{7}=8\frac{1}{3}-6\frac{2}{7}\Leftrightarrow\frac{32}{3}-x:\frac{6}{7}=\frac{25}{3}-\frac{44}{7}\) \(\Leftrightarrow\frac{224}{21}-x:\frac{6}{7}=\frac{75}{21}-\frac{132}{21}\Leftrightarrow-\frac{57}{21}-\frac{224}{21}\)

\(\Leftrightarrow-x:\frac{6}{7}=-\frac{281}{21}\Leftrightarrow-x=-\frac{281}{21}\times\frac{6}{7}\) \(\Leftrightarrow-x=-\frac{1686}{147}\Leftrightarrow x=\frac{562}{49}=11\frac{23}{49}\)

giúp mình với !!!!!!!!!!!!!!!!!!!!!!!!

Câu b, bài b1 chứng minh \(a=2^{2006}-1?\)