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Ta có : 5(x - 2)(x + 3) = 1
=> (5x - 10)(x + 3) = 1
=> 5x2 - 10x + 15x - 30 = 1
=> 5x2 - 5x - 30 = 1
=> 5x(x - 1) = 31
=> x(x - 1) = 31/5 (chịu)
a) Câu này thiếu đề nhé bạn.
b) \(\frac{25}{5^n}=5\)
\(\Rightarrow5^n=25:5\)
\(\Rightarrow5^n=5\)
\(\Rightarrow5^n=5^1\)
\(\Rightarrow n=1\)
Vậy \(n=1.\)
c) \(\frac{81}{\left(-3\right)^n}=-243\)
\(\Rightarrow\left(-3\right)^n=81:\left(-243\right)\)
\(\Rightarrow\left(-3\right)^n=-\frac{1}{3}\)
\(\Rightarrow\left(-3\right)^n=\left(-3\right)^{-1}\)
\(\Rightarrow n=-1\)
Vậy \(n=-1.\)
e) \(\left(\frac{1}{3}\right)^n=\frac{1}{81}\)
\(\Rightarrow\left(\frac{1}{3}\right)^n=\left(\frac{1}{3}\right)^4\)
\(\Rightarrow n=4\)
Vậy \(n=4.\)
f) \(\left(-\frac{3}{4}\right)^n=\frac{81}{256}\)
\(\Rightarrow\left(-\frac{3}{4}\right)^n=\left(-\frac{3}{4}\right)^4\)
\(\Rightarrow n=4\)
Vậy \(n=4.\)
Chúc bạn học tốt!
d) \(\frac{1}{2}.2^n+4.2^n=9.2^5\)
\(\Rightarrow2^n.\left(\frac{1}{2}+4\right)=288\)
\(\Rightarrow2^n.\frac{9}{2}=288\)
\(\Rightarrow2^n=288:\frac{9}{2}\)
\(\Rightarrow2^n=64\)
\(\Rightarrow2^n=2^6\)
\(\Rightarrow n=6\)
Vậy \(n=6.\)
g) \(-\frac{512}{343}=\left(-\frac{8}{7}\right)^n\)
\(\Rightarrow\left(-\frac{8}{7}\right)^n=\left(-\frac{8}{7}\right)^3\)
\(\Rightarrow n=3\)
Vậy \(n=3.\)
h) \(5^{-1}.25^n=125\)
\(\Rightarrow5^{-1}.5^{2n}=5^3\)
\(\Rightarrow5^{-1+2n}=5^3\)
\(\Rightarrow-1+2n=3\)
\(\Rightarrow2n=3+1\)
\(\Rightarrow2n=4\)
\(\Rightarrow n=4:2\)
\(\Rightarrow n=2\)
Vậy \(n=2.\)
k) \(3^{-1}.3^n+6.3^{n-1}=7.3^6\)
\(\Rightarrow3^{n-1}+6.3^{n-1}=7.3^6\)
\(\Rightarrow3^{n-1}.\left(1+6\right)=7.3^6\)
\(\Rightarrow3^{n-1}.7=7.3^6\)
\(\Rightarrow n-1=6\)
\(\Rightarrow n=6+1\)
\(\Rightarrow n=7\)
Vậy \(n=7.\)
Chúc bạn học tốt!
a) 3-2 . 34 . 3n = 37
=> 3-2+4+n = 37
=> 32+n = 37
=> 2 + n = 7
=> n = 5
Vậy n = 5
a) 3-2. 34.3n = 37
3-2 + 4 + n = 37
32 + n = 37
2 + n = 7
n = 5
Vậy n = 5
b) 2-1.2n + 4.2n = 9.25
2n(2-1 + 4) = 9.25
2n. \(\frac{9}{2}\) = 9.25
2n = 9.25 : \(\frac{9}{2}\)
2n = 64
2n = 26
n = 6
Vậy n = 6
c) 32 < 2n < 128
25 < 2n < 27
5 < n < 7
=> n = 6
Vậy n = 6
d) 44 \(\leq \) 4n \(\leq \) 4096
44 \(\leq \) 4n \(\leq \) 46
4 \(\leq \) n \(\leq \) 6
=> n = 5
Vậy n = 5
mk ko chắc câu d nhé
4
a)
\(\Rightarrow3^{-2}.\left(3^3\right)^n=3^n\)
\(\Rightarrow3^{-2}.3^{3n}=3^n\)
\(\Rightarrow3^{3n-2}=3^n\)
\(\Rightarrow3n-2=n\)
\(\Rightarrow n=1\)
b)
\(\Rightarrow3^{4+n-2}=3^7\)
\(\Rightarrow x^{n+2}=3^7\)
\(\Rightarrow n+2=7\)
\(\Rightarrow n=5\)
c)
\(\Rightarrow2^n\left(\frac{1}{2}+4\right)=9.2^5\)
\(\Rightarrow2^n.4,5=9.2^5\)
\(\Rightarrow2^n=2.2^5\)
\(\Rightarrow2^n=2^6\)
\(\Rightarrow n=6\)
d)
\(\Rightarrow\left(2^5\right)^{-n}.\left(2^4\right)^n=2048\)
\(\Rightarrow2^{n-5n}=2^{11}\)
\(\Rightarrow-4n=11\)
\(\Rightarrow n=-\frac{4}{11}\)
nhé
a)(2x-1)6=(2x-1)8
=> (2x-1)8-(2x-1)6=0
=> (2x-1)6.((2x-1)2-1)=0
+)th1(2x-1)6=0
+)th2((2x-1)2-1)=0
a) \(\left(2x-1\right)^6=\left(2x-1\right)^8\)
\(\Rightarrow\left(2x-1\right)\in\left\{\pm1;0\right\}\)
TH1 : \(2x-1=0\) TH2 : \(2x-1=-1\) TH3 : \(2x-1=1\)
\(2x=1\) \(2x=0\) \(2x=2\)
\(x=\frac{1}{2}\) \(x=0\) \(x=1\)
Vậy \(x\in\left\{\frac{1}{2};0;1\right\}\)
b) Tương tự
a,3-1.3n+6.3n-1=7.36
=>3n-1+6.3n-1=7.36
=>3n-1.(1+6)=7.36
=>7.3n-1=7.36
=>n-1=6
=>n=7
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
Bài 1:
a)1/9 x 27n= 3n
1/9=3n:27n
3n:27n=1/9
1n/9n=1/9
=>n=1
\(\frac{1}{2}.2^n+4.2^n=9.2^5\Rightarrow2^n\left(\frac{1}{2}+4\right)=288\Rightarrow2^n.\frac{9}{2}=288\Rightarrow2^{n-2}.9=288\Rightarrow2^{n-2}=32\)(dấu "=>" số 3 bn sửa thành 2n-1.9=288=>2n-1=32 nha)
=>2n-1=25=>n-1=5=>n=5+1=6
vậy......
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