\(\left(x\cdot2,4-4,2\right)\div x=1\)

\(\Rightarrow x\cdot2,4-4,2=x\)

\(\Rightarrow x\cdot2,4=x+4,2\)

\(\Rightarrow\frac{12x}{5}=\frac{5x+21}{5}\)

\(\Rightarrow12x=5x+21\)

\(\Rightarrow12x-5x=21\)

\(\Rightarrow7x=21\Rightarrow x=\frac{21}{7}=3\)

Vậy x = 3 

\(\frac{1}{1\cdot3}+\frac{1}{3\cdot5}+...+\frac{1}{x\left(x+2\right)}\)

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

\(=\frac{1}{2}\cdot\left(1-\frac{1}{x+2}\right)\)

\(=\frac{1}{2}\cdot\frac{x+1}{x+2}\)

\(=\frac{x+1}{2x+2}\)

Đề sai bn ơi :  Sửa : \(\frac{\frac{7}{3}+\frac{7}{4}-\frac{7}{11}}{\frac{5}{3}+\frac{5}{4}-\frac{5}{11}}+\frac{5}{7}\)

\(=\frac{7\cdot\left(\frac{1}{3}+\frac{1}{4}-\frac{1}{11}\right)}{5\cdot\left(\frac{1}{3}+\frac{1}{4}-\frac{1}{11}\right)}+\frac{5}{7}\)

\(=\frac{7}{5}+\frac{5}{7}=\frac{49}{35}+\frac{25}{35}=\frac{74}{35}\)

mn giúp mình nha mình cần đáp án ngay bây giờ

câu a bằng 15/8

câu b bằng 19/6

câu c bằng 3/10

câu d bằng 27/4

a) MSC của 4; 8 và 12 là 24 = \(\dfrac{66}{24}-\dfrac{27}{24}+\dfrac{30}{24}\) =\(\dfrac{69}{24}\) = \(\dfrac{23}{8}\) b) = \(\dfrac{126}{84}\)+\(\dfrac{5}{3}\) =\(\dfrac{3}{2}+\dfrac{5}{3}\) Quy đồng hai p/s ta có: =\(\dfrac{9}{6}+\dfrac{10}{6}\) = \(\dfrac{19}{6}\) c) = \(\dfrac{13}{18}\)x \(\dfrac{9}{5}+1\)

= \(\dfrac{117}{90}+1\) =\(\dfrac{207}{90}\) =\(\dfrac{23}{10}\) d) =3+ \(\dfrac{9}{4}\)x\(\dfrac{5}{3}\) =3+\(\dfrac{45}{12}\) =3+\(\dfrac{15}{4}\) =\(\dfrac{27}{4}\)

bn ê .; là j vậy

1b)\(\frac{7}{19}x\frac{8}{11}+\frac{3}{11}:\frac{19}{7}-\frac{2}{-19}=\frac{7}{19}x\frac{8}{11}+\frac{3}{11}x\frac{7}{19}+\frac{2}{19}=\left(\frac{8}{11}+\frac{3}{11}\right)\frac{7}{19}+\frac{2}{19}=\frac{7}{19}+\frac{2}{19}=\frac{9}{19}\)

c)\(4\left(\frac{4}{9}+\frac{7}{11}-\frac{4}{9}\right)=4\frac{7}{11}\)

từ rồi làm tiếp

2)

a)\(\frac{5}{6}-x=-\frac{5}{12}-\frac{1}{-4}=-\frac{5}{12}+\frac{1}{4}=-\frac{5}{12}+\frac{3}{12}=-\frac{1}{6}.\)

\(x=\frac{5}{6}--\frac{1}{6}=\frac{5}{6}+\frac{1}{6}=1\)

b)\(\frac{x-2}{-5}=\frac{6}{7}\)

\(\frac{\left(x-2\right)\left(-7\right)}{35}=\frac{30}{35}\)

\(\Rightarrow\left(x-2\right)\left(-7\right)=30\)

c)\(\frac{1}{2}x-\frac{3}{4}x=-\frac{5}{6}\)

\(\left(\frac{1}{2}-\frac{3}{4}\right)x=-\frac{5}{6}\)

\(-\frac{1}{4}x=-\frac{5}{6}\)

\(x=\frac{20}{6}=\frac{10}{3}\)

vậy \(x=\frac{10}{3}\)

Cần chi tiết hum bẹn

a) = 76/35 ; 37/9

b) 143/40 ; 19/15

c) 2/3 ; 42/5

d) 21/4 ; 4/7 

a, 11/7 + 3/5

= \(\dfrac{11x5}{7x5}+\dfrac{3x7}{5x7}=\dfrac{55}{35}+\dfrac{21}{35}=\dfrac{76}{35}\)

4 + 1/9

= \(\dfrac{4}{1}+\dfrac{1}{9}=\dfrac{4x9}{1x9}+\dfrac{1x1}{9x1}=\dfrac{36}{9}+\dfrac{1}{9}=\dfrac{37}{9}\)

b, 21/5 - 5/8

= \(\dfrac{21x8}{5x8}-\dfrac{5x5}{8x5}=\dfrac{168}{40}-\dfrac{25}{40}=\dfrac{143}{40}\)

2 - 11/15

=\(\dfrac{2}{1}-\dfrac{11}{15}=\dfrac{30}{15}-\dfrac{11}{15}=\dfrac{19}{15}\)

MIK LÀM ĐC NGẦN ĐẤY THUI BẸN THÔNG CẢM

a.-1,75-(-\(\dfrac{1}{9}\)-2\(\dfrac{1}{8}\))
-1,75-\(\dfrac{1}{9}+\dfrac{17}{8}\)
\(-\dfrac{7}{4}-\dfrac{1}{9}+\dfrac{17}{8}\)
\(\dfrac{-126}{72}-\dfrac{8}{72}+\dfrac{153}{72}\)
=\(\dfrac{19}{72}\)

b.\(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\dfrac{21}{8}+\dfrac{1}{3}\)
\(\dfrac{-2}{24}-\dfrac{63}{24}+\dfrac{64}{24}\)
=\(\dfrac{-1}{24}\)

\(\dfrac{-5}{6}-\left(\dfrac{-3}{8}+\dfrac{1}{10}\right)\)
\(\dfrac{-5}{6}-\dfrac{-3}{8}-\dfrac{1}{10}\)
 

BÀI 1

a,  \(5\times\frac{-7}{10}=\frac{-35}{10}=\frac{-7}{2}\)

b,  \(\frac{4}{5}\times\frac{-7}{10}=\frac{-28}{50}=\frac{-14}{25}\)

c,  \(\frac{4}{9}+\frac{4}{3}\times\frac{16}{4}=\frac{4}{9}+\frac{16}{3}=\frac{52}{9}\)

d,  \(\frac{11}{22}-\frac{3}{9}\times\frac{14}{21}=\frac{11}{22}-\frac{2}{9}=\frac{55}{198}=\frac{5}{18}\)  

BÀI 2

\(A=\frac{6}{13}\times\frac{5}{7}+\frac{6}{13}\times\frac{2}{7}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{17}{13}\)

\(A=\frac{30}{91}+\frac{12}{91}+\frac{119}{91}\)

\(A=\frac{161}{91}=\frac{23}{13}\)

\(B=\frac{11}{15}\times\frac{4}{11}+\frac{11}{15}\times\frac{5}{11}+\frac{11}{15}\times\frac{2}{11}\)

\(B=\frac{4}{15}+\frac{1}{3}+\frac{2}{15}\)

\(B=\frac{11}{15}\)

\(C=\left(\frac{19}{64}-\frac{33}{22}+\frac{24}{51}\right)\times\left(\frac{1}{5}-\frac{1}{15}-\frac{2}{15}\right)\)

\(C=\frac{-797}{1088}\times0\)

\(C=0\)

\(D=\frac{8}{13}\times\frac{7}{12}+\frac{8}{13}\times\frac{5}{12}-\frac{1}{12}\)

\(D=\frac{14}{39}+\frac{10}{39}-\frac{1}{12}\)

\(D=\frac{83}{156}\)

bạn biết câu náy không (24 + 11) . {546 - [14 . (64 - 2^{3}3) : 2]} =

1.

a) \(\frac{-7}{9}.2\frac{3}{4}=\frac{-7}{9}.\frac{11}{4}=\frac{-77}{36}\)

b) \(\frac{2}{3}+\frac{1}{3}.\frac{-2}{5}=\frac{2}{3}+\frac{-2}{15}=\frac{8}{15}\)

c) \(\frac{3}{4}.15\frac{1}{3}-\frac{3}{4}.43\frac{1}{3}=\frac{3}{4}.\frac{46}{3}-\frac{3}{4}.\frac{130}{3}=\frac{23}{2}-\frac{65}{2}=-21\)

d) \(\left(-49,1\right).\frac{13}{27}-58,9.\frac{13}{27}=\frac{13}{27}.\left(-49,1-58,9\right)=\frac{13}{27}.\left(-108\right)=-52\)

e) \(0,375:\left(-4,5\right)=\frac{-1}{12}\)

f) \(3\frac{1}{7}:\left(-1\frac{3}{7}\right)=\frac{22}{7}:\frac{-10}{7}=\frac{-11}{5}\)

g) \(9\frac{1}{3}:4\frac{2}{3}-2=\frac{28}{3}:\frac{14}{3}-2=2-2=0\)

h) \(\left(7\frac{3}{4}:0,3125+4,5.2\frac{2}{45}\right):\left(-8,5\right)=\left(\frac{31}{4}:\frac{5}{16}+\frac{9}{2}.\frac{92}{45}\right):\frac{-17}{2}=\left(\frac{124}{5}+\frac{46}{5}\right):\frac{-17}{2}=34:\frac{-17}{2}=-4\)

Bài 1 : Tính:

a)

\(\frac{-7}{9}.2\frac{3}{4}=\frac{-7}{9}.\frac{11}{4}=\frac{-77}{36}\)

b) 

\(\frac{2}{3}+\frac{1}{3}.\frac{-2}{5}=\frac{2}{3}+\frac{-2}{15}=\frac{10}{15}+\frac{-2}{15}=\frac{8}{15}\)

c)

\(\frac{3}{4}.15\frac{1}{3}-\frac{3}{4}.43\frac{1}{3}=\frac{3}{4}.\frac{46}{3}-\frac{3}{4}.\frac{130}{3}\)\(=\frac{23}{2}-\frac{65}{2}=\frac{-42}{2}=-21\)

....

Tự lm tiếp dạng như v

Bài 2 : 

\(A=\frac{-6}{11}.\frac{7}{10}.\frac{11}{-6}.-20=\left(\frac{-6}{11}.\frac{11}{-6}\right).\left(\frac{7}{10}.-20\right)\)\(=1.\left(-14\right)=-14\)

.....

Bài 3 : 

\(\frac{3}{7}.x-\frac{2}{5}.x=\frac{-17}{35}\)

\(\Leftrightarrow\frac{3}{7}-\frac{2}{5}.x=\frac{-17}{35}\)

\(\Leftrightarrow\frac{1}{35}x=\frac{-17}{35}\)

\(\Leftrightarrow x=\frac{-17}{35}:\frac{1}{35}\)

\(\Leftrightarrow x=\frac{-17}{35}.35=-17\)