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\(\frac{x}{2}=\frac{y}{3}\Rightarrow\frac{x}{14}=\frac{y}{21}\)
\(\frac{y}{7}=\frac{z}{4}\Rightarrow\frac{y}{21}=\frac{z}{12}\)
\(\Leftrightarrow\frac{x}{14}=\frac{y}{21}=\frac{z}{12}=\frac{x+y-z}{14+21-12}=\frac{69}{23}=3\)
\(\Rightarrow x=52;y=63;z=36\)
\(\hept{\begin{cases}\frac{x}{2}=\frac{y}{3}\\\frac{y}{7}=\frac{z}{4}\end{cases}\Rightarrow\hept{\begin{cases}\frac{x}{14}=\frac{y}{21}\\\frac{y}{21}=\frac{z}{12}\end{cases}\Rightarrow}\frac{x}{14}=\frac{y}{21}=\frac{z}{12}}\)
Áp dụng tính chất dãy tỉ số bằng nhau:
\(\frac{x}{14}=\frac{y}{21}=\frac{z}{12}=\frac{x+y-z}{14+21-12}=\frac{69}{23}=3\)
\(\Rightarrow\hept{\begin{cases}x=3.14=42\\y=3.21=63\\z=3.12=36\end{cases}}\)
\(\frac{5}{x-2}=\frac{15}{6}\)
\(\Rightarrow15x-30=30\)
\(15x=60\)
\(x=4\)
\(\Rightarrow\frac{x+1+y+2+z+3}{3+4+5}\)
\(\Rightarrow\frac{24}{12}=2\)
\(\frac{x+1}{3}=2\Rightarrow x=5\)
\(\frac{y+2}{4}=2\Rightarrow y=6\)
\(\frac{z+3}{5}=2\Rightarrow z=7\)
a/ \(\Rightarrow\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=-2187\Rightarrow\left(-3\right)^n=\left(-3\right)^7\Rightarrow n=7\)
b/ \(\Rightarrow-\frac{3}{8}-x+\frac{5}{6}=\frac{4}{3}\Rightarrow\frac{11}{24}-x=\frac{4}{3}\Rightarrow x=-\frac{7}{8}\)
a)\(5^x.\left(5^3\right)^2=625\)
\(5^x.5^6=5^4\)
\(5^x=5^{-2}\)
\(x=-2\)
b)\(27< 81^3:3^x< 243\)
\(3^3< \left(3^4\right)^3:3^x< 3^5\)
\(3^3< 3^{12}:3^x< 3^5\)
\(3^{12}:3^x=3^4\)
\(3^x=3^3\)
\(x=3\)
c)\(\left(5x+1\right)^2=\frac{36}{49}\)
\(\left(5x+1\right)^2=\left(\frac{6}{7}\right)^2\)
\(5x+1=\frac{6}{7}\)
\(5x=\frac{-1}{7}\)
\(x=\frac{-1}{35}\)
d)\(\left(x-\frac{2}{9}\right)^3=\left(\frac{2}{3}\right)^6\)
\(\left(x-\frac{2}{9}\right)^3=\left[\left(\frac{2}{3}\right)^2\right]^3\)
\(x-\frac{2}{9}=\frac{4}{9}\)
\(x=\frac{6}{9}=\frac{2}{3}\)
\(5^x.\left(5^3\right)^2=625\)
\(\Rightarrow5^x.5^6=5^4\)
\(\Rightarrow5^{x+6}=5^4\Rightarrow x+6=4\Rightarrow x=-2\)
Đề sai rồi bạn : Phải là :
\(5^x:\left(5^3\right)^2=625\)
\(\Rightarrow5^x:5^6=5^4\)
\(\Rightarrow5^{x-6}=5^4\)
\(\Rightarrow x-6=4\Rightarrow x=10\)
Nhứng nếu đề đúng thì bạn có thể lấy KQ trên
a) \(\left(\frac{4}{9}\right)^x=\left(\frac{8}{27}\right)^6\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{2x}=\left(\frac{2}{3}\right)^{18}\)
\(\Leftrightarrow2x=18\)
\(\Leftrightarrow x=9\)
b) \(\left(\frac{1}{9}\right)^x=\left(\frac{1}{27}\right)^{22}\)
\(\Leftrightarrow\left(\frac{1}{9}\right)^x=\left(\frac{1}{3}\right)^{66}\)
\(\Leftrightarrow x=66\)
(x - 2/3)3 = -1/27
=> (x - 2/3)3 = (-1/3)3
=> x - 2/3 = -1/3
=> x = -1/3 + 2/3
=> x = 1/3
Từ bài ra ta có \(\left(x-\frac{2}{3}\right)^3=\left(\frac{-1}{3}\right)^3\)
\(\Rightarrow x-\frac{2}{3}=\frac{-1}{3}\)
\(\Rightarrow x=\frac{-1}{3}+\frac{2}{3}\)
\(\Rightarrow x=\frac{1}{3}\)
Vậy ... nếu đúng thì k nha