A bạn ơi cho mình sửa đề một tí câu a phải là \(\dfrac{16}{2^n}=2\)
a) \(\dfrac{16}{2^n}=2\Rightarrow\dfrac{2^4}{2^n}=2\Rightarrow2^{4-n}=2\Rightarrow4-n=1\Rightarrow n=3\)
b) \(\dfrac{\left(-3\right)^n}{81}=-27\Rightarrow\dfrac{\left(-3\right)^n}{\left(-3\right)^4}=\left(-3\right)^3\)
\(\Rightarrow\) \(\left(-3\right)^{n-4}=\left(-3\right)^3\)
\(\Rightarrow n-4=3\Rightarrow n=7\)
c) \(8^n:2^n=4=gt\Rightarrow\left(8:2\right)^n=4=gt\Rightarrow4^n=4=gt\Rightarrow n=1\)
Hok tốt nha!
a) \(\dfrac{16}{2^n}=2\)
\(\Rightarrow\)\(\dfrac{2^4}{2^n}=2\)
\(\Rightarrow\) 2. 2n = 24
2n + 1 = 24
n + 1 = 4
n = 4 - 1
n = 3
b) \(\dfrac{\left(-3\right)^n}{81}=\left(-27\right)\)
\(\Rightarrow\)\(\dfrac{\left(-3\right)^n}{\left(-3\right)^4}=\left(-3\right)^3\)
\(\Rightarrow\) (-3)n = (-3)4 . (-3)3
(-3)n = (-3)7
n = 7
c) 8n : 2n = 4
\(\Rightarrow\)(8 : 2)n = 4
4n = 4
n = 1.