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\(a,\frac{16}{2^n}=2\)
\(\Rightarrow\frac{16}{2^n}=\frac{2}{1}\)
\(\Rightarrow2^n.2=16\)
\(\Rightarrow4^n=4^2\)
\(\Rightarrow n=2\)
\(b,\frac{\left(-3\right)^n}{81}=-27\)
\(\Rightarrow\left(-3\right)^n=81.\left(-27\right)\)
\(\Rightarrow\left(-3\right)^n=-2187\)
\(\Rightarrow\left(-3\right)^n=\left(-3\right)^7\)
\(\Rightarrow n=7\)
a) \(\frac{\left(-3\right)^n}{81}=-27\)
\(\left(-3\right)^n=81.\left(-27\right)\)
\(\left(-3\right)^n=\left(-3\right)^4.\left(-3\right)^3\)
\(\left(-3\right)^n=\left(-3\right)^7\)
\(n=7\)
b)
\(4< 2^n\le2.16\)
\(2^2< 2^n\le2^5\)
\(2< n\le5\)
\(n\in\left\{3;4;5\right\}\)
c)
\(\frac{16^n}{4^n}=1024\)
\(\left(\frac{16}{4}\right)^n=4^5\)
\(4^n=4^5\)
\(n=5\)
Qùa tặng cuộc sống(1 bài)
a) 16 = 2,2n
24 = 2n+1
4 = n+1 => n = 3
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)\(\left(\dfrac{1}{2}\right)^n=\dfrac{1}{32}\)
=>\(\left(\dfrac{1}{2}\right)^n=\left(\dfrac{1}{2}\right)^5\)
=>n=5
b)\(\left(\dfrac{343}{125}\right)=\left(\dfrac{7}{5}\right)^n\)
=>\(\left(\dfrac{7}{5}\right)^3=\left(\dfrac{7}{5}\right)^n\)
=>n=3
c)\(\dfrac{16}{2^n}=2\)
=>2n=\(\dfrac{16}{2}\)
=>2n=8
=>2n=23
=>n=3
d)\(\dfrac{\left(-3\right)^n}{81}=-27\)
=>(-3)n=-27.81
=>(-3)n=-2187
=>(-3)n=(-3)7
=>n=7
e)8n:2n=4
=>(23)n:2n=4
=>23n:2n=4
=>23n-n=4
=>22n=4
=>22n=22
=>2n=2
=>n=1
f)32.3n=35
=>3n=35:32
=>3n=35-2
=>3n=33
=>n=3
g) (22:4).2n=4
=>1.2n=22
=>n=2
h)3-2.34.3n=37
=>\(\left(\dfrac{1}{3}\right)^2\).34.3n=37
=>32.3n=37
=>32+n=37
=>2+n=7
=>n=5
a, \(\dfrac{16}{2^n}=2\)
\(2^n=\dfrac{16}{2}\)
\(2^n=8\)
\(2^n=2^3\)
=> n = 3
b, \(\dfrac{\left(-3\right)^n}{81}=-27\)
\(\left(-3\right)^n=-27\cdot81\)
\(\left(-3\right)^n=\left(-3\right)^3\cdot3^4\)
\(\left(-3\right)^n=\left(-3\right)^7\)
=> n = 7
c, \(8^n:2^n=4\)
\(2^{3n}:2^n=2^2\)
\(2^{2n}=2^2\)
=> 2n = 2
n = 2:2
n = 1
a )
\(\dfrac{16}{2^n}=2\) \(\Leftrightarrow16:x=2\)
\(\Rightarrow x=8\)
\(2^n=8\Rightarrow n=3\)
b )
\(\dfrac{\left(-3\right)^n}{81}=-27\) \(\Leftrightarrow x=-27.81\)
\(\Rightarrow x=-2187\)
\(\left(-3\right)^n=-2187\Rightarrow n=7\)
c )
\(8^n:2^n=4\Leftrightarrow4^n=4\)
\(\Rightarrow n=1\)
a . 16 / 2^x = 2
= > 16 : 2^x = 2
=> 2^4 : 2^x = 2^1
=> x = 3
b . ( -3 )^x/ 81 = -27
=> -3 ^ x = -27 . 81
= > -3^x = -2187
=> -3^ x = -3^7
=> x = 7
c . 8^ x : 2^x = 4
=> 4 ^ x = 4
=> x = 1
a) 16/2^n = 2
2^n = 16 : 2
2^n = 8
2^n = 2^3
=> n = 3
b) (-3)^n/81 = -27
(-3)^n = 81 : (-27)
(-3)^n = -3
=> n = 1
c) 8^n : 2^n = 4
(8 : 2)^n = 4
4^n = 4
=> n = 1