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O
3
LM
Lê Minh Vũ
VIP
5 tháng 7 2023
\(\dfrac{x-17}{33}+\dfrac{x-21}{29}+\dfrac{x}{25}=4\)
\(\dfrac{x-17}{33}+\dfrac{x-21}{29}+\dfrac{x}{25}-4=0\)
\(\dfrac{\left(x-17\right)\times725}{33\times725}+\dfrac{\left(x-21\right)\times825}{29\times825}+\dfrac{x\times957}{25\times957}-\dfrac{4\times23925}{23925}=0\)
\(725x-12325+825x-17325+957x-95700=0\)
\(2507x-125350=0\)
\(2507x=125350\)
\(x=50\)
LM
Lê Minh Vũ
VIP
5 tháng 7 2023
Nếu mà theo cách x - 50 = 0 thì bạn theo cách này nha:
\(\dfrac{x-17}{33}+\dfrac{x-21}{29}+\dfrac{x}{25}=4\)
\(\dfrac{x-17}{33}+\dfrac{x-21}{29}+\dfrac{x}{25}-4=0\)
\(\dfrac{x-17}{33}-1+\dfrac{x-21}{29}-1+\dfrac{x}{25}-2=0\)
\(\dfrac{x-50}{33}+\dfrac{x-50}{29}+\dfrac{x-50}{25}=0\)
\(\left(x-50\right)\left(\dfrac{1}{33}+\dfrac{1}{29}+\dfrac{1}{5}\right)=0\)
Vì \(\dfrac{1}{33}+\dfrac{1}{29}+\dfrac{1}{25}>0\)
=> \(x-50=0\)
=> \(x=50\)
L
1
28 tháng 6 2018
\(\dfrac{x+32}{11}+\dfrac{x+33}{12}=\dfrac{x+34}{13}+\dfrac{x+35}{14}\)
\(\Leftrightarrow\left(\dfrac{x+32}{11}-1\right)+\left(\dfrac{x+33}{12}-1\right)=\left(\dfrac{x+34}{13}-1\right)+\left(\dfrac{x+35}{14}-1\right)\)
\(\Leftrightarrow\dfrac{x+21}{11}+\dfrac{x+21}{12}=\dfrac{x+21}{13}+\dfrac{x+21}{14}\)
\(\Leftrightarrow\dfrac{x+21}{11}+\dfrac{x+21}{12}-\dfrac{x+21}{13}-\dfrac{x+21}{14}=0\)
\(\Leftrightarrow\left(x+21\right)\left(\dfrac{1}{11}+\dfrac{1}{12}-\dfrac{1}{13}-\dfrac{1}{14}\right)=0\)
Mà \(\dfrac{1}{11}+\dfrac{1}{12}-\dfrac{1}{13}-\dfrac{1}{14}\ne0\)
\(\Leftrightarrow x+21=0\)
\(\Leftrightarrow x=-21\)
Vậy ..
NV
2
7 tháng 12 2021
\(1,\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{x+y}{2+5}=\dfrac{21}{7}=3\\ \Rightarrow\left\{{}\begin{matrix}x=6\\y=15\end{matrix}\right.\\ 2,7x=3y\Rightarrow\dfrac{x}{3}=\dfrac{y}{7}=\dfrac{x-y}{3-7}=\dfrac{16}{-4}=-4\\ \Rightarrow\left\{{}\begin{matrix}x=-12\\y=-28\end{matrix}\right.\\ 3,\dfrac{x}{5}=\dfrac{y}{6}=\dfrac{z}{7}=\dfrac{x-y-z}{5-6-7}=\dfrac{36}{-8}=-\dfrac{9}{2}\\ \Rightarrow\left\{{}\begin{matrix}x=-\dfrac{45}{2}\\y=-27\\z=-\dfrac{63}{2}\end{matrix}\right.\\ 4,x:y:z=3:5:7\Rightarrow\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{z}{7}=\dfrac{2x+3y-z}{6+15-7}=\dfrac{-14}{14}=-1\\ \Rightarrow\left\{{}\begin{matrix}x=-3\\y=-5\\z=-7\end{matrix}\right.\)
7 tháng 12 2021
3. Áp dụng tính chất dãy tỉ số bằng nhau, ta có:
\(\dfrac{x}{5}=\dfrac{y}{6}=\dfrac{z}{7}=\dfrac{x-y-z}{5-6-7}=\dfrac{36}{-8}=\dfrac{-9}{2}\)
\(x=\dfrac{-45}{2}\)
\(y=-27\)
\(z=\dfrac{-63}{2}\)
`21/14=33/x`
`=>21*x=33*14`
`=>21x=462`
`=>x=462:21`
`=>x=22`
x=14.33/21=22