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a)\(11\frac{1}{4}-\left(2\frac{5}{7}+5\frac{1}{4}\right)\)
\(=\frac{45}{4}-\left(\frac{19}{7}+\frac{21}{4}\right)\)
\(=\frac{45}{4}-\left(\frac{76}{28}+\frac{147}{28}\right)\)
\(=\frac{45}{4}-\frac{223}{28}\)
\(=\frac{315}{28}-\frac{223}{28}\)
\(=\frac{23}{7}\)
b) \(\left(8\frac{5}{11}+3\frac{5}{8}\right)-3\frac{5}{11}\)
\(=\left(\frac{93}{11}+\frac{29}{8}\right)-\frac{38}{11}\)
\(=\left(\frac{744}{88}+\frac{319}{88}\right)-\frac{38}{11}\)
\(=\frac{1063}{88}-\frac{38}{11}=\frac{1063}{88}-\frac{304}{88}\)
\(=\frac{69}{8}\)
\(\frac{3}{x}+\frac{4}{3}=\frac{5}{6}\)
\(\frac{3}{x}=\frac{5}{6}-\frac{4}{3}\)
\(\frac{3}{x}=\frac{-1}{2}\)
\(\Rightarrow3.2=\left(-1\right).x\)
\(\Rightarrow6=\left(-1\right).x\)
\(\Rightarrow x=6:\left(-1\right)\)
\(\Rightarrow x=-6\)
\(\frac{x}{2}-\frac{2}{y}=\frac{1}{2}\)
\(\Rightarrow\frac{x}{2}-\frac{1}{2}=\frac{2}{y}\)
\(\Rightarrow\frac{x-1}{2}=\frac{2}{y}\)
\(\Rightarrow\hept{\begin{cases}x-1=2\\2=y\end{cases}\Rightarrow}\hept{\begin{cases}x=3\\y=2\end{cases}}\)
\(b,\frac{3}{x}+\frac{4}{3}=\frac{5}{6}\)
\(\Rightarrow\frac{3}{x}=\frac{5}{6}-\frac{4}{3}\)
\(\Rightarrow\frac{3}{x}=\frac{5}{6}-\frac{8}{6}\)
\(\Rightarrow\frac{3}{x}=\frac{-3}{6}\)
\(\Rightarrow x\cdot(-3)=18\Rightarrow x=-6\)
\(a,\frac{x-1}{9}=\frac{8}{3}\)
\(\Leftrightarrow x-1=24\)
\(\Rightarrow x=25\)
\(b,-\frac{x}{4}=-\frac{9}{x}\)
\(\Leftrightarrow x^2=36\)
\(\Leftrightarrow\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)
\(c,\frac{x}{4}=\frac{18}{x+1}\)
\(\Leftrightarrow x^2+x=72\)
\(\Leftrightarrow x\left(x+1\right)=72..\)
ấn nhầm: lm tiếp nhé!
\(x\left(x+1\right)=72\)
\(\text{Mà x thuộc Z nên }x\left(x+1\right)=8\left(8+1\right)\)
\(\Leftrightarrow x=8\)
\(A=8\frac{4}{17}-\left(2\frac{5}{9}+3\frac{4}{17}\right)\)
\(A=8\frac{4}{17}-2\frac{5}{9}-3\frac{4}{17}\)
\(A=\left(8\frac{4}{17}-3\frac{4}{17}\right)-\frac{23}{9}\)
\(A=5-\frac{23}{9}\)
\(A=\frac{45}{9}-\frac{23}{9}\)
\(A=\frac{22}{9}\)
\(A=8\frac{4}{7}-2\frac{5}{9}-3\frac{4}{7}\)
\(A=\left(8\frac{4}{7}-3\frac{4}{7}\right)-2\frac{5}{9}\)
\(A=5-2\frac{5}{9}\)
\(A=4+1-2\frac{5}{9}\)
\(A=4+1-\frac{23}{9}\)
\(A=4+\frac{-14}{9}\)
\(A=1\frac{5}{9}\)
Dấu " . " k p dấu " , "
a) \(\frac{91}{1\cdot4}+\frac{91}{4\cdot7}+\frac{91}{7\cdot10}+...+\frac{91}{88\cdot99}\)
* Bài đúng k z ???
b) \(5\frac{1}{7}\left(3\frac{2}{3}+4\frac{1}{7}\right)=\frac{36}{7}\cdot\left(\frac{11}{3}+\frac{29}{7}\right)\)
\(=\frac{36}{7}\cdot\frac{164}{21}=\frac{1968}{49}\)
Trả lời
a)
\(x^2:\frac{16}{11}=\frac{11}{4}\)
\(\Leftrightarrow x^2=\frac{11}{4}\cdot\frac{16}{11}\)
\(\Leftrightarrow x^2=\frac{16}{4}\)
\(\Leftrightarrow x^2=\left(\frac{4}{2}\right)^2\)
\(\Leftrightarrow x=\frac{4}{2}\)
Vậy x=\(\frac{4}{2}\)
b) (bạn thiếu nhóm \(\frac{1}{10\cdot13}\))
Đặt \(A=\frac{1}{1\cdot4}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+\frac{1}{10\cdot13}+\frac{1}{13\cdot16}+\frac{1}{16\cdot19}\)
\(\Rightarrow3A=3\left(\frac{1}{1\cdot4}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+\frac{1}{10\cdot13}+\frac{1}{13\cdot16}+\frac{1}{16\cdot19}\right)\)
\(\Rightarrow3A=\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{3}{7\cdot10}+\frac{3}{10\cdot13}+\frac{3}{13\cdot16}+\frac{3}{16\cdot19}\)
\(\Rightarrow3A=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}+\frac{1}{16}-\frac{1}{19}+\frac{1}{19}\)
\(\Rightarrow3A=1-\frac{1}{19}\Leftrightarrow3A=\frac{18}{19}\)
\(\Rightarrow A=\frac{18}{19}:3\Leftrightarrow A=\frac{6}{19}\)
Cs phải cái đề như này ko e : 6,5 - 4/9 : | x/4 + 1/3 | = 2 ( dấu ":" dấu chia )