\(\frac{3}{y-7}=\frac{27}{135}\)
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Bài làm
\(C=-\frac{3}{5}.\frac{20}{135}.\frac{-7}{1400}.\frac{250}{3}.\frac{27}{10}\)
\(C=\frac{-3}{5}.\frac{4}{27}.\frac{-1}{200}.\frac{250}{3}.\frac{27}{10}\)
\(C=\frac{-3.4.\left(-1\right).250.27}{5.27.200.3.10}\)
\(C=\frac{1}{10}\)
Vậy \(C=\frac{1}{10}\)
# Học tốt #
C = \(\frac{-3}{5}\cdot\frac{20}{135}\cdot\frac{-7}{1400}\cdot\frac{250}{3}\cdot\frac{27}{10}\) C = \(\left(\frac{-3}{5}\cdot\frac{250}{3}\right)\cdot\left(\frac{20}{135}\cdot\frac{27}{10}\right)\cdot\frac{-7}{1400}\) C = \(-50\cdot\frac{2}{5}\cdot\frac{-7}{1400}\) C = \(-20\cdot\frac{-7}{1400}\) C = \(\frac{1}{10}\)
Bài làm:
Đặt \(\frac{x}{7}=\frac{y}{5}=\frac{z}{3}=k\)
=> \(\hept{\begin{cases}x=7k\\y=5k\\z=3k\end{cases}}\)
Mà \(yz=135\Leftrightarrow15k^2=135\Leftrightarrow k^2=9\Rightarrow k=\pm3\)
=> \(\hept{\begin{cases}x=\pm21\\y=\pm15\\z=\pm9\end{cases}}\)
Đặt \(\frac{x}{7}=\frac{y}{5}=\frac{z}{3}=k\Rightarrow\hept{\begin{cases}x=7k\\y=5k\\z=3k\end{cases}}\)
Khi đó yz = 135
<=> 5k.3k = 135
=> 15.k2 = 135
=> k2 = 9
=> k = \(\pm\)3
Nếu k = 3 => x = 21 ; y = 15 ; z = 9
Nếu k = -3 => x = -21 ; y = -15 ; z = -9
Vậy các cặp (x;y;z) thỏa mãn bài toán là (21 ; 15 ; 9) ; (-21 ; - 15 ; -9)
\(\left(2018-\frac{2}{135}+\frac{1}{50}\right)-\left(1-\frac{7}{135}+\frac{4}{50}\right)-\left(5+\frac{5}{135}+\frac{3}{50}\right)\)
\(=2018-\frac{2}{135}+\frac{1}{50}-1+\frac{7}{135}-\frac{4}{50}-5-\frac{5}{135}-\frac{3}{50}\)
\(=2012-\frac{6}{50}\)
\(c)\) \(C=\frac{\frac{2}{7}+\frac{2}{5}+\frac{2}{17}-\frac{2}{293}}{\frac{3}{7}+\frac{3}{5}+\frac{3}{17}-\frac{3}{293}}\)
\(C=\frac{2\left(\frac{1}{7}+\frac{1}{5}+\frac{1}{17}-\frac{1}{293}\right)}{3\left(\frac{1}{7}+\frac{1}{5}+\frac{1}{17}-\frac{1}{193}\right)}\)
\(C=\frac{2}{3}\)
Bạn Cô nàng Thiên Bình làm đúng hết òi =.=
a=7.[1/8+1/27-1/49]
------------------------
11.[1/8+1/27-1/49]
=7/11
cau b,c tuong tu nha h mk
a) 3/x-7 = 27/135
3/x-7 = 3/15
x - 7 = 15
x = 15 + 7
x = 22
a) \(\frac{3}{x-7}=\frac{27}{135}\)
\(\Rightarrow\)\(\left(x-7\right).27=3.135\)
\(\Rightarrow\)\(\left(x-7\right).27=405\)
\(\Rightarrow\)\(x-7=15\)
\(\Rightarrow\)\(x=22\)
Vậy \(x=22\)
b ) \(71+65.4=\frac{x+140}{x}+260\)
\(71+260=\frac{x+140}{x}+260\)
\(331=\frac{x+140}{x}+260\)
\(331-260=\frac{x+140}{x}\)
\(71=\frac{x+140}{x}\)
\(71=\frac{x}{x}+\frac{140}{x}\)
\(71=1+\frac{140}{x}\)
\(70=\frac{140}{x}\)
\(x=140\div70\)
\(x=20\)
Vậy \(x=20\)
#TQY
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{2}{3}y-\dfrac{5}{3}x+5-\dfrac{1}{4}y-\dfrac{27}{4}+2x=0\\\dfrac{1}{3}x+\dfrac{1}{3}+y-\dfrac{6}{7}y+\dfrac{5}{7}x=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{3}x+\dfrac{1}{28}y=-5\\\dfrac{22}{21}x+\dfrac{1}{7}y=-\dfrac{1}{3}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}28x+3y=-420\\88x+12y=-28\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}112x+12y=-420\\88x+12y=-28\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}24x=-392\\28x+3y=-420\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{49}{3}\\y=\dfrac{112}{9}\end{matrix}\right.\)
\(\frac{3}{22-7}=\frac{27}{135}\)
NHO K CHO MK NHA
CHUC BAN HOC TOT ^_^
\(\frac{3}{y-27}=\frac{27}{135}\)
\(\Rightarrow\frac{3}{y-27}=\frac{1}{5}\)
\(\Rightarrow y-27=3.5\)
\(\Rightarrow y-27=15\)
\(\Rightarrow y=15+27\)
\(\Rightarrow y=42\)
Vậy y = 42
_Chúc bạn học tốt_