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7/48 - (1/2 x 2 + 1/6 x 4 + 1/8 x 5 + 1/12 x 7 + 1/14 x 8) : x = 0
7/48 - (1 + 2/3 + 5/8 + 7/12 + 4/7) : x = 0 (đã rút gọn)
7/48 - (336/336 + 224/336 + 210/336 + 196/336 + 192/336) : x = 0 (quy đồng)
7/48 - 193/56 : x = 0
193/56 : x = 0 + 7/48
193/56 : x = 7/48
x = 193/56 : 7/48
x = 1158/49
\(\dfrac{2}{3}\times\left(x+\dfrac{4}{5}\right)=\dfrac{-1}{3}\\ x+\dfrac{4}{5}=\dfrac{-1}{3}:\dfrac{2}{3}\\ x+\dfrac{4}{5}=\dfrac{-1}{3}\times\dfrac{3}{2}\\ x+\dfrac{4}{5}=\dfrac{-1}{2}\\ x=\dfrac{-1}{2}-\dfrac{4}{5}\\ x=\dfrac{-5}{10}-\dfrac{8}{10}\\ x=\dfrac{-13}{10}\)
\(\dfrac{2}{3}.\left(x+\dfrac{4}{5}\right)=-\dfrac{1}{3}\)
\(\left(x+\dfrac{4}{5}\right)=\left(-\dfrac{1}{3}:\dfrac{2}{3}\right)\)
\(\left(x+\dfrac{4}{5}\right)=\left(-\dfrac{1}{3}.\dfrac{3}{2}\right)=-\dfrac{1}{2}\)
\(x\) \(=\left(-\dfrac{1}{2}\right)-\dfrac{4}{5}\)
\(x\) \(=\left(-\dfrac{1}{2}\right)+\left(-\dfrac{4}{5}\right)\)
\(x\) \(=-\dfrac{13}{10}\)
Bài làm:
Ta có: \(\frac{1}{1.3}+\frac{1}{2.4}+\frac{1}{3.5}+...+\frac{1}{98.100}\)
\(=\left(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{97.99}\right)+\left(\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{98.100}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{97}-\frac{1}{99}\right)+\frac{1}{2}\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{98}-\frac{1}{100}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{99}\right)+\frac{1}{2}\left(\frac{1}{2}-\frac{1}{100}\right)\)
\(=\frac{1}{2}.\frac{98}{99}+\frac{1}{2}.\frac{49}{100}\)
\(=\frac{49}{99}+\frac{49}{200}\)
\(=\frac{14651}{19800}\)
\(\Leftrightarrow x-\dfrac{1}{4}=\dfrac{20}{27}\)
hay x=20/27+1/4=107/108
\(\dfrac{x-1}{4}=\dfrac{5}{3}.\dfrac{4}{9}\Leftrightarrow\dfrac{x-1}{4}=\dfrac{20}{27}\Rightarrow27x-27=80\)
\(\Leftrightarrow27x=107\Leftrightarrow x=\dfrac{107}{27}\)
\(x-\dfrac{1}{4}=\dfrac{5}{3}\times\dfrac{4}{9}\\ \Rightarrow x-\dfrac{1}{4}=\dfrac{20}{27}\\ \Rightarrow x=\dfrac{20}{27}+\dfrac{1}{4}\\ \Rightarrow x=\dfrac{107}{108}\)
\(x-\dfrac{1}{4}=\dfrac{5}{6}\times\dfrac{4}{9}\)
<=>\(x-\dfrac{1}{4}=\dfrac{10}{27}\)
<=>\(x=\dfrac{10}{27}+\dfrac{1}{4}=\dfrac{67}{108}\)
Bạn nên gõ đúng phân số cần giải nha . Nếu cần thiết thì bạn có thể sử dụng công thức trực quan hoặc cho thêm dấu ngoặc vào phần tử hoặc mẫu số khi nó có từ 2 phần tử trở lên á bạn .
\(\dfrac{2x-3}{3}+\dfrac{-3}{2}=\dfrac{1}{3}\)
\(\dfrac{2x-3}{3}=\dfrac{1}{3}+\dfrac{3}{2}\)
\(\dfrac{2x-3}{3}=\dfrac{11}{6}\)
\(\dfrac{2.\left(2x-3\right)}{3.2}=\dfrac{11}{6}\)
\(2\left(2x-3\right)=11\)
\(4x-6=11\)
\(x=\dfrac{17}{4}\)
2x-\(\dfrac{3}{3}\)+\(\dfrac{-3}{2}\)=\(\dfrac{1}{3}\)
=>2x-1=\(\dfrac{1}{3}\)+\(\dfrac{3}{2}\)=\(\dfrac{11}{6}\)
=>2x=\(\dfrac{11}{6}\)+1=\(\dfrac{17}{6}\)
=>x=\(\dfrac{17}{6}\):2=\(\dfrac{17}{4}\)
x:1/2+3/4=5/4
đấp số:5/4
5/4.chuc ban hoc gioi