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a, \(\dfrac{15\times14-1}{13\times15+14}\)
= \(\dfrac{15\times\left(13+1\right)-1}{13\times15+14}\)
= \(\dfrac{13\times15+15-1}{13\times15+14}\)
= \(\dfrac{13\times15+14}{13\times15+14}\)
= 1
c, \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(9+1\right)\times\left\{\left(9-1\right):1+1\right\}:2}{10}\)
= \(\dfrac{10\times9:2}{10}\)
= \(\dfrac{9}{2}\)
\(\left(\dfrac{5}{6}+\dfrac{7}{x}\right)-\dfrac{16}{12}=\dfrac{2}{3}\)
\(\Rightarrow\dfrac{5}{6}+\dfrac{7}{x}=\dfrac{2}{3}+\dfrac{16}{12}=\dfrac{8}{12}+\dfrac{16}{12}=\dfrac{24}{12}=2\)
\(\Rightarrow\dfrac{7}{x}=2-\dfrac{5}{6}=\dfrac{12}{6}-\dfrac{5}{6}=\dfrac{7}{6}\)
=> x = 6
(\(\dfrac{5}{6}\) + \(\dfrac{7}{x}\)) - \(\dfrac{16}{12}\) = \(\dfrac{2}{3}\)
\(\dfrac{5}{6}\) + \(\dfrac{7}{x}\) = \(\dfrac{2}{3}\) + \(\dfrac{16}{12}\)
\(\dfrac{5}{6}\) + \(\dfrac{7}{x}\) = 2
\(\dfrac{7}{x}\) = 2 - \(\dfrac{5}{6}\)
\(\dfrac{7}{x}\) = \(\dfrac{1}{6}\)
\(x\) = 6 x (7 : 1)
\(x\) = 6 x 7
\(x\) = 42
#Yu
a)x*4/5:2=6/7 b)6/5:x:5/4=10/15
x*4/5=6/7 x 2 6/5:x=10/15 x 5/4
x*4/5=12/7 6/5:x=5/6
x=12/7:4/5 x=6/5:5/6
x=15/7 x=36/25
a) x * 4/5 : 2 = 6/7
x * 4/5 = 6/7 *2
x *4/5 = 12/7
x = 12/7 : 4/5
x = 15/7
Vậy x = 15/7
lên gg nghe thầy cô giảng cho dể hiểu chứ tụi mình ghi ra bạn đọc cũng hiểu sơ sơ thôi
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k biết
\(\dfrac{1818}{4343}\times\dfrac{43}{6}=\dfrac{18}{43}\times\dfrac{43}{6}=\dfrac{18}{6}=3\)