Tìm Y biết :
1 / 5 + 3 / 5 : y = 24/25
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\(a,\frac{42}{25}:\frac{y}{5}=\frac{6}{5}\)
\(\frac{y}{5}=\frac{42}{25}:\frac{6}{5}\)
\(\frac{y}{5}=\frac{42}{25}\times\frac{5}{6}\)
\(\frac{y}{5}=\frac{7}{5}\)
\(\Leftrightarrow5y=7.5\)
\(5y=35\)
\(y=7\)
\((x-6)(3x-9)>0\)
TH1:
\(\orbr{\begin{cases}x-6< 0\\3x-9< 0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x< 6\\x< 3\end{cases}}\)\(\Rightarrow x< 3\)
TH2:
\(\orbr{\begin{cases}x-6>0\\3x-9>0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x>6\\x>3\end{cases}}\)\(\Rightarrow x>6\)
Vậy \(x< 3\) hoặc \(x>6\)thì \((x-6)(3x-9)>0\)
Học tốt!
20.
\((2x-1)(6-x)>0\)
TH1:
\(\orbr{\begin{cases}2x-1>0\\6-x>0\end{cases}\Rightarrow\orbr{\begin{cases}x< \frac{1}{2}\\x< 6\end{cases}}\Rightarrow x< 6}\)
TH2
\(\orbr{\begin{cases}2x-1< 0\\6-x< 0\end{cases}\Rightarrow\orbr{\begin{cases}x>\frac{1}{2}\\x>6\end{cases}}\Rightarrow x>\frac{1}{2}}\)
Vậy \(x< 6\)hoặc \(x>\frac{1}{2}\)thì \((2x-1)(6-x)>0\)
24/y=3/5*8/3
24/y=8/5
24:y=8/5
y=24;8/5
y=15
b,42/25:y/5=6/7
y/5=42/25:6/7
y/5=49/25
y:5=49/25
y=49/25*5
y=49/5=9,8
\(\frac{24}{y}:\frac{8}{3}=\frac{3}{5}\)
\(\Rightarrow\frac{24}{y}=\frac{3}{5}\times\frac{8}{3}\)
\(\Rightarrow\frac{24}{y}=\frac{8}{5}\)
\(\Rightarrow y=\frac{8}{5}\times24=\frac{192}{5}\)
b , \(\frac{42}{25}:\frac{y}{5}=\frac{6}{7}\)
\(\Rightarrow\frac{y}{5}=\frac{6}{7}\times\frac{42}{25}=\frac{36}{25}\)
\(\Rightarrow y=\frac{36}{25}\times5=\frac{36}{5}\)
\(\frac{x-2}{27}+\frac{x-3}{26}+\frac{x-4}{25}+\frac{x-5}{24}+\frac{x-44}{5}=1\)
\(\Leftrightarrow\left(\frac{x-2}{27}-1\right)+\left(\frac{x-3}{26}-1\right)+\left(\frac{x-4}{25}-1\right)+\left(\frac{x-5}{24}-1\right)\)\(+\left(\frac{x-44}{5}+3\right)=1-1\)
\(\Leftrightarrow\frac{x-29}{27}+\frac{x-29}{26}+\frac{x-29}{25}+\frac{x-29}{24}\)\(+\frac{x-29}{5}=0\)
\(\Leftrightarrow\left(x-29\right)\left(\frac{1}{27}+\frac{1}{26}+\frac{1}{25}+\frac{1}{24}+\frac{1}{5}\right)=0\)
Mà \(\frac{1}{27}+\frac{1}{26}+\frac{1}{25}+\frac{1}{24}+\frac{1}{5}\ne0\)
=> x - 29 = 0
=> x = 29.
\(\frac{1}{5}\)+ \(\frac{3}{5}y\)=\(\frac{24}{25}\)
suy ra 3/5y =24/25-1/5
suy ra 3/5y =19/25
suy ra y = 19/25:3/5
suy ra y = 19/15