Question

Tìm x,biết: 

a) \(\frac{16}{2^x}=1\)

b) \(5^{x+2}=625\)

c) \(\frac{x+3}{8}=\frac{2}{x-3}\)

d) \(\frac{x^2}{6}=\frac{24}{25}\)

Answer 1

a) \(\frac{16}{2^x}=1\Leftrightarrow2^x=16\Leftrightarrow2^x=2^4\Leftrightarrow x=4\)

b)\(5^{x+2}=625\Leftrightarrow5^{x+2}=5^4\Leftrightarrow x+2=4\Leftrightarrow x=2\)

c)\(\frac{x+3}{8}=\frac{2}{x-3}\left(đk:x\ne3\right)\Leftrightarrow\left(x+3\right).\left(x-3\right)=2.8\Leftrightarrow x^2-9=16\Leftrightarrow x^2=25\Leftrightarrow\orbr{\begin{cases}x=5\\x=-5\end{cases}}\)

d)\(\frac{x^2}{6}=\frac{24}{25}\Leftrightarrow25x^2=24.6\Leftrightarrow\left(5x\right)^2=144\Leftrightarrow\orbr{\begin{cases}5x=12\\5x=-12\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{12}{5}\\x=-\frac{12}{5}\end{cases}}\)

Answer 2

a) 16=2^x \(\Leftrightarrow\)x=4

b)5^x+2=5^4\(\Leftrightarrow\)x+2=4\(\Leftrightarrow\)x=2

k đi, mk làm tiếp cho