tính nhanh phân số sau
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(\frac{3}{4}\times\frac{8}{5}\times\frac{5}{9}=\frac{3\times8\times5}{4\times5\times9}=\frac{3\times4\times2\times5}{4\times5\times3\times3}=\frac{2}{3}\)
\(\frac{3}{4}\times\frac{8}{5}\times\frac{5}{9}=\frac{3\times8\times5}{4\times5\times9}=\frac{3\times4\times2\times5}{4\times5\times3\times3}=\frac{2}{3}\)
\(2009+2009\times99\)
\(=2009\times\left(99+1\right)\)
\(=2009\times100\)
\(=200900\)
\(=\dfrac{0.125\cdot8\cdot25}{16\cdot0.0625\cdot45-20}=\dfrac{25}{45-20}=1\)
\(=\frac{3}{4}+\frac{6}{7}+\frac{19}{32}+\frac{1}{4}+\frac{1}{7}+\frac{13}{32}\)
\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{6}{7}+\frac{1}{7}\right)+\left(\frac{19}{32}+\frac{13}{32}\right)=1+1+1=3\)
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+....+\frac{2}{x\left(x+1\right)}=\frac{499}{999}\)
\(\Leftrightarrow\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+....+\frac{2}{x\left(x+1\right)}=\frac{499}{999}\)
\(\Leftrightarrow\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+....+\frac{2}{x\left(x+1\right)}=\frac{499}{999}\)
\(\Leftrightarrow2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{499}{999}\)
\(\Leftrightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{499}{999}\div2\)
\(\Leftrightarrow\frac{1}{x+1}=\frac{1}{2}-\frac{499}{1998}\)
\(\Leftrightarrow\frac{1}{x+1}=\frac{250}{999}\)
\(\Leftrightarrow\left(x+1\right).250=999\Rightarrow x+1=\frac{999}{250}\Rightarrow x=\frac{999}{250}-1=\frac{749}{250}\)
Như kiểu đề sai hay sao ý
\(\frac{15}{3}\)= 15 : 3 = 5
\(\frac{28}{4}\)= 28 : 4 = 7
\(\dfrac{27}{12}+\dfrac{17}{6}+\dfrac{25}{36}-\dfrac{15}{6}\)
\(=\dfrac{9}{4}+\dfrac{17}{6}+\dfrac{25}{36}-\dfrac{5}{2}\)
\(=\dfrac{81}{36}+\dfrac{102}{36}+\dfrac{25}{36}-\dfrac{90}{36}\)
\(=\dfrac{118}{36}=\dfrac{59}{18}\)