\(A=\frac{15\times3^{11}+4\times27^4}{9^7}\)

\(A=\frac{15\times177147+4\times531441}{4782969}\)

\(A=\frac{2657205+2125764}{4782969}\)

\(A=\frac{47829969}{47829969}=1\)

Tự nhiên phần Σ của tớ bị lỗi nên tớ tính tử số rồi tính mẫu nhé :

Tử số của A :

15 x 3¹¹ + 4 x 27⁴

= 5 x 3¹² + 4 x 3¹²

= 3¹² x ( 5 + 4 ) 

= 3¹² x 9 

= 3¹² x 3²

= 3¹⁴

Mẫu số của A :

97 = (3²)⁷ = 3^{2 x 7} = 3¹⁴

Vậy A = 3¹⁴ : 3¹⁴ = 1

\(B=\frac{\frac{7}{12}+\frac{5}{6}-1}{5-\frac{3}{4}+\frac{1}{3}}\)

\(B=\frac{\frac{7}{12}+\frac{10}{12}-\frac{12}{12}}{\frac{60}{12}-\frac{9}{12}+\frac{4}{12}}\)

\(B=\frac{\frac{5}{12}}{\frac{55}{12}}\)

\(B=\frac{1}{11}\)

Đặt \(\frac{x}{2}=\frac{2y}{5}=\frac{3z}{7}=k\)

\(\Rightarrow\hept{\begin{cases}x=2k\\y=\frac{5}{2}k\\z=\frac{7k}{3}\end{cases}}\)

Thay vô rồi tính tiếp nhé!

bạn có thể nói rõ hơn ko?

Mk chưa hiểu lắm

Đặt \(\frac{x}{2}=\frac{2y}{5}=\frac{3z}{7}=k\)

\(\Rightarrow\hept{\begin{cases}x=2k\\y=\frac{5k}{2}\\z=\frac{7k}{3}\end{cases}}\)

\(\Rightarrow A=\frac{2.2k+5.\frac{5k}{2}-3.\frac{7k}{3}}{7.2k+\frac{5k}{2}-5.\frac{7k}{3}}\)

\(=\frac{-3k+\frac{25k}{2}}{14k-\frac{55k}{6}}\)

\(=\frac{19k.6}{2.29k}=\frac{57}{29}\)

Ý là vậy :P

ta có

đặt 3/5+3/7-3/11=N=> N=3*(1/5+1/7-1/11)
đặt 4/5+4/7-4/11=P=> P=4*(1/5+1/7-1/11)

=> N/P=3*(1/5+1/7-1/11)/4*(1/5+1/7-1/11)=> M=3/4

cảm ơn bạn ngọc hằng nha bạn học giỏi thật

a) \(\frac{{ - 3}}{7}.\frac{2}{5} + \frac{2}{5}.\left( { - \frac{5}{{14}}} \right) - \frac{{18}}{{35}}\)

\(\begin{array}{l} = \frac{2}{5}.\left( {\frac{{ - 3}}{7} + \frac{{ - 5}}{{14}}} \right) - \frac{{18}}{{35}}\\ = \frac{2}{5}.\left( {\frac{{ - 6}}{{14}} + \frac{{ - 5}}{{14}}} \right) - \frac{{18}}{{35}}\\ = \frac{2}{5}.\frac{{ - 11}}{{14}} - \frac{{18}}{{35}} = \frac{{ - 11}}{{35}} - \frac{{18}}{{35}} =  \frac{{ -29}}{{35}}\end{array}\)

b) \(\left( {\frac{2}{3} - \frac{5}{{11}} + \frac{1}{4}} \right):\left( {1 + \frac{5}{{12}} - \frac{7}{{11}}} \right)\)

\(\begin{array}{l} = \left( {\frac{{2.11.4}}{{3.11.4}} - \frac{{5.3.4}}{{11.3.4}} + \frac{{1.3.11}}{{4.3.11}}} \right):\left( {\frac{11.12}{11.12} + \frac{{5.11}}{{12.11}} - \frac{{7.12}}{{11.12}}} \right)\\ = \left( {\frac{{88 - 60 + 33}}{{121}}} \right):\left( { \frac{{121+55 - 84}}{{121}}} \right)\\ = \frac{{61}}{{121}}:\frac{{92}}{{121}} = \frac{{61}}{{121}}.\frac{{121}}{{92}}= \frac{{61}}{{92}}\end{array}\)

c) \(\left( {13,6 - 37,8} \right).\left( { - 3,2} \right)\)

\( = \left( { - 24,2} \right).\left( { - 3,2} \right) = 77,44\)

d) \(\left( { - 25,4} \right).\left( {18,5 + 43,6 - 16,8} \right):12,7\)

\(\begin{array}{l} = \left( { - 25,4} \right).\left( {62,1 - 16,8} \right):12,7\\ = \left( { - 25,4} \right).45,3:12,7\\ = \left( { - 25,4} \right):12,7.45,3\\ =  (- 2).45,3 =  - 90,6\end{array}\)

a: \(=\dfrac{2}{5}\cdot\left(-\dfrac{3}{7}-\dfrac{5}{14}\right)-\dfrac{18}{35}\)

\(=\dfrac{2}{5}\cdot\dfrac{-6-5}{14}-\dfrac{18}{35}\)

\(=\dfrac{2}{5}\cdot\dfrac{-11}{14}-\dfrac{18}{35}=-\dfrac{22}{70}-\dfrac{18}{35}=\dfrac{-58}{70}=-\dfrac{29}{35}\)

b: \(=\dfrac{88-60+33}{132}:\dfrac{132+55-84}{132}\)

\(=\dfrac{61}{132}\cdot\dfrac{132}{103}=\dfrac{61}{103}\)

c: \(=-24.2\cdot\left(-3.2\right)=24.2\cdot3.2=77.44\)

d: \(=\dfrac{-25.4}{12.7}\cdot45.3=-2\cdot45.3=-90.6\)

khó thấy quá bạn ơi

Kết quả là 8/9

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