bài2 \(x\times\dfrac{15}{16}-x\times\dfrac{4}{16}=2\) 

     \(x\times\dfrac{11}{16}=2\) 

     \(x=2:\dfrac{11}{16}\) 

    \(x=\dfrac{32}{11}\)

Bài 1 : 

 \(\dfrac{x}{16}\times\left(2017-1\right)=2\)

          \(\dfrac{x}{16}\times2016=2\)

                      \(\dfrac{x}{16}=\dfrac{2}{2016}\)

                         \(x=\dfrac{2}{2016}\times16\)

                         \(x=\dfrac{1}{63}\)

1- (5\(\dfrac{4}{9}\) +x+7\(\dfrac{7}{18}\)) : 15\(\dfrac{3}{4}\) = 0 

1- (\(\dfrac{49}{9}+x+\dfrac{133}{18}\)) : \(\dfrac{63}{4}=0\) 

 (\(\dfrac{49}{9}+\dfrac{133}{18}\)+\(x\) ) : \(\dfrac{63}{4}\) = 1 - 0 

       (\(\dfrac{77}{6}\) + \(x\) ) : \(\dfrac{63}{4}\) = 1

         \(\dfrac{77}{6}+x\)         = 1 x \(\dfrac{63}{4}\) 

          \(\dfrac{77}{6}\) + \(x\)          = \(\dfrac{63}{4}\)

                  \(x\)            = \(\dfrac{63}{4}\) - \(\dfrac{77}{6}\)

                  \(x=\) \(\dfrac{35}{12}\)

a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)

\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)

=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)

b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)

\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)

Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)

c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)

\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)

=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)

d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)

\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6

=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)

1 ) l x l = 5 => x thuộc { -5 ; 5 }

Vậy x thuộc { - 5 ; 5 Ư]

2 ) l x l = 5 + 7 - 10

    l x l  = 2 => x thuộc { - 2 ; 2 }

Vậy x thuộc { - 2 ; 2 }

3 ) l x l = - 5 - l - 10 l + 15

     l x l = - 5 - 10 + 15

     l x l = 0 => x = 0

Vậy x = 0

4 ) l x l = - ( - 12 ) + ( - 15 ) + 8

     l x l = 12 + ( - 15 ) + 8

     l x l = - 3 + 8

     l x l = 5 => x thuộc { -5 ; 5 }

Vậy x thuộc { - 5 ; 5 }

1)!x!=5

=>x=5 hay x=-5

Vậy x=5 hay x=-5

Các câu khác thì tương tự nên bạn tự làm nhé!

Tìm x biết:

a,x-1/2 =2/15

x=2/15 + 1/2

x =19/30

Vậy x =19/30

b,5 và 3/4 +x =15 - 2 và 1/2

23/4 + x  =27/2

x =27/2 - 23/4

x=31/4

Vậy x =31/4

c,x : 14,1 =0,25

x =0,25.14,1

x=3,525

Vậy x = 3.525

d,x + 1/2.1/3 =3/4

x + 1/6 =3/4

x =3/4 - 1/6

x =7/12

Vậy x = 7/12

a)\(x=\frac{2}{15}+\frac{1}{2}=\frac{4+1}{15x2}=\frac{5}{30}=\frac{1}{6}\)

b)anh chưa hiểu lắm hỗn số à em

c)\(x=\frac{1}{4}x\frac{141}{10}=\frac{141}{40}=3,525\)

d)\(x+\frac{1}{6}=\frac{3}{4}\)

suy ra: \(x=\frac{3}{4}-\frac{1}{6}=\frac{18-4}{24}=\frac{14}{24}=\frac{7}{12}\)

a x - 1\2 = 2\15

x            =2\15 + 1\2

x            =19\30

b 23\4 + x =27\2

x               =27\2-23\4

x                =31\4

c x :14,1=0,25

x            =0,25 x 14 ,1

x            =3,525

d x +1\2 .1\3 =3\4

x+1\6 =3\4

x        =3\4-1\6

x        =7\12

Bài 1:

Chiều rộng hcn đó là:

\(\dfrac{4}{3}\times\dfrac{1}{2}=\dfrac{2}{3}\) ( m )

Chu vi hình chữ nhật đó là:

\(\left(\dfrac{4}{3}+\dfrac{2}{3}\right)\times2=4\left(m\right)\)

Đ/s: 4 m

Bài 2:

\(\dfrac{2}{5}+\dfrac{1}{3}:\dfrac{2}{3}=\dfrac{2}{5}+\dfrac{1}{3}\times\dfrac{3}{2}=\dfrac{2}{5}+\dfrac{1}{2}=\dfrac{4}{10}+\dfrac{5}{10}=\dfrac{9}{10}\)

Bài 3;

\(\Rightarrow\dfrac{3}{4}+x\times\dfrac{5}{2}=\dfrac{37}{16}\\ \Rightarrow x\times\dfrac{5}{2}=\dfrac{37}{16}-\dfrac{3}{4}=\dfrac{25}{16}\\ \Rightarrow x=\dfrac{25}{16}\times\dfrac{2}{5}=\dfrac{5}{8}\)

Bài 4:

\(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}=\dfrac{15}{16}\)

Bài 5:

\(\Rightarrow x\times\dfrac{2}{5}=\dfrac{4}{7}\\ \Rightarrow x=\dfrac{4}{7}\times\dfrac{5}{2}=\dfrac{10}{7}\)

\(\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x.\left(x+1\right)}=\frac{4}{15}\)( đã sửa đề từ x+(x+1) thành x.(x+1) )

\(\Rightarrow\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{4}{15}\)( Áp dụng \(\frac{1}{a.\left(a+1\right)}=\frac{1}{a}-\frac{1}{a+1}\))

\(\Rightarrow\frac{1}{3}-\frac{1}{x+1}=\frac{4}{15}\)

\(\Rightarrow\frac{x+1-3}{3.\left(x+1\right)}=\frac{4}{15}\)

\(\Rightarrow\frac{x-2}{3x+3}=\frac{4}{15}\)

\(\Rightarrow4.\left(3x+3\right)=15.\left(x-2\right)\)

\(\Rightarrow12x+12=15x-30\)

\(\Rightarrow12x=15x-30-12\)

\(\Rightarrow12x-15x=-30-12\)

\(\Rightarrow-3x=-42\)

\(\Rightarrow x=14\)

3 x 15 + 21 x 15 + 85 x 5

= 45 + 315 + 425

= 785

15 - 30 + 40 

= 25

21 + 19 - 50 + 10

= 0

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=-\dfrac{1}{20}+2\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{12}\times\dfrac{3}{12}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=-\dfrac{9}{20}\)

\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)

\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)

\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)

\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)

\(=\dfrac{44}{20}-\dfrac{5}{20}\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)

\(=\dfrac{6}{20}-\dfrac{15}{20}\)

\(=-\dfrac{9}{20}\)

Help meeeeeeeeeee

v

\(\dfrac{11}{4}-\dfrac{9}{8}=\dfrac{22-9}{8}=\dfrac{13}{8}+\dfrac{15}{12}=\dfrac{156+120}{96}=\dfrac{276}{96}\)

\(\dfrac{126}{84}+\dfrac{5}{3}=\dfrac{378+420}{252}=\dfrac{798}{252}\)

\(\dfrac{13}{18}:\dfrac{5}{9}=\dfrac{13.5}{18.9}=\dfrac{615}{162}-\dfrac{1}{1}=\dfrac{615-162}{162}=\dfrac{453}{162}\)

\(\dfrac{3}{9}+\dfrac{45}{12}=\dfrac{36+405}{108}=\dfrac{441}{108}\)

a,11/4−9/8+15/12

=    13/8    + 15/12 

=  276/96

= 29/8

b,6/7x21/12+5/3

=  126/84 +  5/3

=   798/252

=         

c,13/18:5/9−1

=   615/162- 1

=  453/162

d,3+9/4:3/5

=  3 + 45/12

= 441/108