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
