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a, 16/2n=2
<=>2n=8
<=>n=4
b, (-3)^n =-27*81=-2187
n=7( vì (-3)^7 =-2187
c, 8^n : 2^n =4
<=> (8:2)^n=4
4^n=4
n=1
\(a,\frac{16}{2^n}=2\Rightarrow2^n=16:2\Rightarrow2^n=8\Rightarrow2^n=2^3\Rightarrow n=3\)
\(b,\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=81.\left(-27\right)\Rightarrow\left(-3\right)^n=-2187\Rightarrow3^n=3^7\Rightarrow n=7\)
\(c,8^n:2^n=4\Rightarrow4^n=4\Rightarrow n=1\)
\(a,\frac{16}{2^n}=2\) \(b,\frac{\left(-3\right)^n}{81}=-27\) \(c,8^n:2^n=4\)
\(\Rightarrow2^4=2^n.2\) \(\Rightarrow\left(-3\right)^n=\left(-27\right).81\) \(\Rightarrow\left(8:2\right)^n=4\)
\(\Rightarrow4=n+1\) \(\Rightarrow\left(-3\right)^n=\left(-3\right)^7\) \(\Rightarrow4^n=4\)
\(\Rightarrow n=4-1=3\) \(\Rightarrow n=7\) \(\Rightarrow n=1\)
Tìm số tự nhiên n, biết:
a) \(\frac{16}{2^n}=2\)
b) \(\frac{\left(-3\right)^n}{81}=-27\)
c) \(8^n:2^2\)
a) \(\frac{16}{2^n}=2\)
=> 16 = 2 . 2n
=> 16 = 2n+1
=> 24 = 2n+1
=> n + 1 = 4
=> n = 4 - 1
=> n = 3
Vậy n = 3
b) \(\frac{\left(-3\right)^n}{81}=-27\)
=> (-3)n = -27 . 81
=> (-3)n = (-3)3 . (-3)4
=> (-3)n = (-3)7
=> n = 7
Vậy n = 7
c) 8n : 22 = bao nhiêu vậy ban?
Chuk bn hk tốt!
a)\(\frac{16}{2^n}=2\)
\(\Rightarrow16:2=2^n\)
2n=8=23
Vậy n=3
b)\(\frac{\left(-3\right)^n}{81}=-27\)
\(\Rightarrow\)(-3)n=-27.81
(-3)n=-2187=(-3)7
Vậy n=7
c)Mk ko hiểu bn ghi gì
\(a,\frac{16}{2^n}=2=>\frac{2^4}{2^n}=2=>2^4:2^n=2=>2^{4-n}=2=>4-n=1=>n=3\)
\(b,\frac{\left(-3\right)^n}{81}=-27=>\frac{\left(-3\right)^n}{3^4}=\left(-3\right)^3=>\frac{\left(-3\right)^n}{\left(-3\right)^4}=\left(-3\right)^3=>\left(-3\right)^{n-4}=\left(-3\right)^3=>n-4=3=>n=7\)
\(c,8^n:2^n=4=>\left(8:2\right)^n=4=>4^n=4=>n=1\)
c, \(\frac{-32}{-2^n}=4\)
\(\Rightarrow-2^n=-32:4\)
\(\Rightarrow-2^n=-8\)
\(\Rightarrow-2^n=-2^3\Rightarrow n=3\)
d, \(\frac{8}{2^n}=2\)
\(\Rightarrow2^n=8:2\)
\(\Rightarrow2^n=4\)
\(\Rightarrow2^n=2^2\Rightarrow n=2\)
e, \(\frac{25^3}{5^n}=25\)
\(\Rightarrow5^n=25^3:25\)
\(\Rightarrow5^n=25^2\)
\(\Rightarrow5^n=5^4\Rightarrow n=4\)
i , \(8^{10}:2^n=4^5\)
\(\Rightarrow2^n=8^{10}:4^5\)
\(\Rightarrow2^n=\left(2^3\right)^{10}:\left(2^2\right)^5\)
\(\Rightarrow2^n=2^{30}:2^{10}\)
\(\Rightarrow2^n=2^{20}\Rightarrow n=20\)
k, \(2^n.81^4=27^{10}\)
\(\Rightarrow2^n=27^{10}:81^4\)
\(\Rightarrow2^n=\left(3^3\right)^{10}:\left(3^4\right)^4\)
\(\Rightarrow2^n=3^{30}:3^{16}\)
\(\Rightarrow2^n=3^{14}\)
\(\Rightarrow2^n=4782969\)Không chia hết cho 2 nên ko có Gt n thỏa mãn
\(\frac{16}{2^n}=2\Rightarrow2^n=16:2\Rightarrow2^n=8\Rightarrow n=3\)
\(\frac{\left(-3\right)^n}{81}=-27\Rightarrow\left(-3\right)^n=\left(-27\right).81\Rightarrow\left(-3\right)^n=-2187\Rightarrow n=7\)
\(8^n:2^n=4\Rightarrow\left(8:2\right)^n=4\Rightarrow4^n=4\Rightarrow n=1\)
a) => 2n = 16/2 = 8
=> n = 3
b) => (-3)n = -27 x 81 = -2187
=> n = 7
c) 8n : 2n = ( 8 : 2)n = 4n = 4
=> n = 1
a) 3^1=3
3^4=81
3^5=243
vậy n=1 đến 5
b)2^(2n-3).2^(8-2n)=2^[2n-3+(8-2n)]=2^(2n-3+8-2n)=2^5
16=2^4<2^n<2^5
n= không có
A! Bạn ơi! Bạn có thể giải thích câu a đc hong. Mình không hiểu cho lắm...
a)
\(\frac{16}{2^x}=2\)
\(\Rightarrow2^{x+1}=16\)
\(\Rightarrow2^{x+1}=2^4\)
\(\Rightarrow x+1=4\)
\(\Rightarrow x=3\)
b)
\(\frac{\left(-3\right)^x}{81}=-27\)
\(\Rightarrow\left(-3\right)^x=-\left(3^3.3^4\right)\)
\(\Rightarrow-3^x=-3^7\)
=> x=7
c)
\(8^n:2^n=4\)
\(\Rightarrow2^{3n}:2^n=4\)
\(\Rightarrow2^{3n-n}=4\)
\(\Rightarrow2^{2n}=2^2\)
=>2n=2
=>n=1
a)\(\frac{16}{2^n}=2\)
=>16:2n=2
=>2n=16:2
=>2n=8
b)ko nhớ cách làm
c)8n:2n=4
=>(23)n:2n=22
=>23n:2n=22
=>23n-n=22
=>22n=22
=>2n=2
=>n=1
dc rùi chứ