(11 / 29 + 2 / 29 + 16 / 29 ) . 9 / 10

1 . 9/10 = 9/10

\(\dfrac{9}{10}\times\left(\dfrac{11}{29}+\dfrac{2}{29}+\dfrac{16}{29}\right)=\dfrac{9}{10}\times\dfrac{29}{29}=\dfrac{9}{10}\times1=\dfrac{9}{10}\)

= 9/10 x ( 11/29 + 2/9 + 16/29 )

= 9/10 x 1

= 9/10

\(\frac{x+5}{13}+\frac{x+6}{12}+\frac{x+7}{11}=\frac{x+8}{10}+\frac{x+9}{9}+\frac{x+10}{8}\)

\(\Leftrightarrow\left(\frac{x+5}{13}+1\right)+\left(\frac{x+6}{12}+1\right)+\left(\frac{x+7}{11}+1\right)=\left(\frac{x+8}{10}+1\right)+\left(\frac{x+9}{9}+1\right)+\left(\frac{x+10}{8}\right)\)

\(\Leftrightarrow\frac{x+18}{13}+\frac{x+18}{12}+\frac{x+18}{11}=\frac{x+18}{10}+\frac{x+18}{9}+\frac{x+18}{8}\)

ta chuyển về vế trái được 

\(\Leftrightarrow\left(x+18\right)\left(\frac{1}{13}+\frac{1}{122}+\frac{1}{11}-\frac{1}{10}-\frac{1}{9}-\frac{1}{8}\right)=0\)

\(\Leftrightarrow x+2018=0\)(do cái còn lại khác 0)

\(\Leftrightarrow x=-2018\)

mình nghĩ đề cậu viết thiếu mình sửa rồi

Ta có:

\(\frac{x+5}{13}+\frac{x+6}{12}+\frac{x+7}{11}=\frac{x+8}{10}+\frac{x+9}{9}+\frac{x+10}{8}\)

\(\Rightarrow\left(\frac{x+5}{13}+1\right)+\left(\frac{x+6}{12}+1\right)+\left(\frac{x+7}{11}+1\right)=\left(\frac{x+8}{10}+1\right)+\left(\frac{x+9}{9}+1\right)+\left(\frac{x+10}{8}+1\right)\)

\(\Rightarrow\frac{x+18}{13}+\frac{x+18}{12}+\frac{x+18}{11}=\frac{x+18}{10}+\frac{x+18}{9}+\frac{x+18}{8}\)

\(\Rightarrow\frac{x+18}{13}+\frac{x+18}{12}+\frac{x+18}{11}-\frac{x+18}{10}-\frac{x+18}{9}-\frac{x+18}{8}=0\)

\(\Rightarrow\left(x+18\right)\times\left(\frac{1}{13}+\frac{1}{12}+\frac{1}{11}-\frac{1}{10}-\frac{1}{9}-\frac{1}{8}\right)=0\)

Vì \(\frac{1}{13}+\frac{1}{12}+\frac{1}{11}-\frac{1}{10}-\frac{1}{9}-\frac{1}{8}\ne0\)

\(\Rightarrow x+18=0\)

\(\Rightarrow x=-18\)

Vậy phương trình có nghiệm là x = -18

xin lỗi vì tớ nhầm một chút ở dòng cuối cho mình xin lỗi nhé

Bài làm

m) (x + 2).(3 - x) = 0;     

=> x + 2 = 0 hoặc 3 - x = 0

=> x = -2 hoặc x = 3

Vậy x = -2 hoặc x = 3   

d) 5¹¹.7¹² + 5¹¹.7¹¹ 

= 5¹¹ . ( 7¹² + 7¹¹ )

= 5¹¹ . [ 7¹¹ . ( 7 + 1 ) ]

= 5¹¹ . 7¹¹ . 8

= ( 5 . 7 )¹¹ . 8

= 35¹¹ . 8

5¹².7¹² + 9.5¹¹.7¹¹ 

= 5¹¹ ( 5 . 7¹² + 9 . 1 . 7¹¹ )

= 5¹¹ [ 7¹¹ ( 5 . 7 + 9 . 1 . 1 ) ]

= 5¹¹ ( 7¹¹ . 44 )

= 5¹¹ . 7¹¹ . 44

= 35¹¹ . 44

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

d. \(\frac{5^{11}.7^{12}+5^{11}.7^{11}}{5^{12}.7^{12}+9.5^{11}.7^{11}}=\frac{5^{11}.\left(7^{12}+7^{11}\right)}{5^{11}.\left(5.7^{12}+9.7^{11}\right)}=\frac{7^{12}+7^{11}}{5.7^{12}+9.7^{11}}=\frac{1}{5.9}=\frac{1}{45}\)

q. \(\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+...+10+11=11\)

\(\Rightarrow\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+...+10=0\)

\(\Rightarrow\left[\left(x-3\right)+\left(x-2\right)+\left(x-1\right)\right]+(1+2+3+...+10)=0\)

\(\Rightarrow\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+55=0\)

\(\Rightarrow x-3+x-2+x-1=-55\)

\(\Rightarrow3x-6=-55\)

\(\Rightarrow3x=-49\)

\(\Rightarrow x=-\frac{49}{3}\)

các bạn tốt quá mình cám ơn rất nhiều

[6: 3/5 - 7/6 x 6/7] : [ 21/5 x 10/11 + 57/11]

= 9 : 9

= 1 

\(\left(6:\frac{3}{5}-\frac{7}{6}\times\frac{6}{7}\right):\left(\frac{21}{5}\times\frac{10}{11}+\frac{57}{11}\right)\)

\(=\left(10-1\right):\left(\frac{42}{11}+\frac{57}{11}\right)\)

\(=9:9\)

\(=1\)

\(\left(6\div\frac{3}{5}-\frac{7}{6}\times\frac{6}{7}\right)\div\left(\frac{21}{5}\times\frac{10}{11}+\frac{57}{11}\right)\)

\(=\left(6\times\frac{5}{3}-1\right)\div\left(\frac{42}{11}+\frac{57}{11}\right)\)

\(=\frac{13}{5}\div9\)

\(=\frac{13}{45}\)

a. $\dfrac{14}{15}+\dfrac{2}{11}+\dfrac{1}{15}+\dfrac{4}{11}+\dfrac{10}{22}$

$=(\dfrac{14}{15}+dfrac{1}{15})+(\dfrac{2}{11}+\dfrac{4}{11}+\dfrac{10}{22})$

$=1+1=2$

b. $74\times43-43+27\times43$

$=(74-1+27)\times43$

$=100\times43=4300$

\(a)\dfrac{14}{15}+\dfrac{2}{11}+\dfrac{1}{15}+\dfrac{4}{11}+\dfrac{10}{22}\)

\(=\left(\dfrac{14}{15}+\dfrac{1}{15}\right)+\dfrac{2}{11}+\dfrac{4}{11}+\dfrac{5}{11}\)

\(=1+1=2\)

\(b)74\times43-43+27\times43\)

\(=43\times\left(74-1+27\right)\)

\(=43\times100=4300\)

a) \(\dfrac{14}{15}+\dfrac{2}{11}+\dfrac{1}{15}+\dfrac{4}{11}+\dfrac{10}{22}\)

= \(\left(\dfrac{14}{15}+\dfrac{1}{15}\right)+\left(\dfrac{2}{11}+\dfrac{4}{11}\right)+\dfrac{5}{11}\)

= \(1+\dfrac{6}{11}+\dfrac{5}{11}\)

= 2

b) 74 x 43 - 43 + 27 x 43

= 74 x 43 - 43 x 1 + 27 x 43

= 43 x ( 74 - 1 + 27 )

= 43 x 100

= 4300

6/20:3=6/20x1/3=6/60=1/10

11h-8h30p=2h30p=2.5h

10 7/10-4 3/10

=107/10-43/10

=64/10=32/5

chúc bn học tốt!

11) \(\sqrt{\dfrac{3}{4}x}-\dfrac{1}{2}=\dfrac{3}{7}\left(x\ge0\right)\)

\(\Rightarrow\sqrt{\dfrac{3}{4}x}=\dfrac{3}{7}+\dfrac{1}{2}\)

\(\Rightarrow\sqrt{\dfrac{3}{4}x}=\dfrac{13}{14}\)

\(\Rightarrow\dfrac{3}{4}x=\left(\dfrac{13}{14}\right)^2\)

\(\Rightarrow\dfrac{3}{4}x=\dfrac{169}{196}\)

\(\Rightarrow x=\dfrac{169}{196}:\dfrac{3}{4}\)

\(\Rightarrow x=\dfrac{169}{147}\)

12) \(\dfrac{2}{3}+\sqrt{\dfrac{1}{3}:x}=\dfrac{3}{5}\left(x>0\right)\)

\(\Rightarrow\sqrt{\dfrac{1}{3}:x}=\dfrac{3}{5}-\dfrac{2}{3}\)

\(\Rightarrow\sqrt{\dfrac{1}{3}:x}=-\dfrac{1}{15}\) 

Do biểu thức trong dấu căn luôn dương nên không có x thỏa mãn