K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Các câu hỏi dưới đây có thể giống với câu hỏi trên
QD
27 tháng 7 2017
h) \(5^x+5^{x+2}=650\)
\(\Leftrightarrow5^x+5^x.5^2=650\)
\(\Leftrightarrow5^x\left(1+25\right)=650\)
\(\Leftrightarrow5^x.26=650\)
\(\Leftrightarrow5^x=25\)
\(\Leftrightarrow x=2\)
haizzz,đăng ít thôi,chứ nhìn hoa mắt quá =.=
DG
1 tháng 8 2017
bây định làm j ở chỗ này vậy??? có j ib ns vs nhao chớ sao ns ở đây
22 tháng 5 2022
1: \(\left(\dfrac{1}{16}\right)^x=\left(\dfrac{1}{8}\right)^6\)
\(\Leftrightarrow\left(\dfrac{1}{2}\right)^{4x}=\left(\dfrac{1}{2}\right)^{18}\)
=>4x=18
hay x=9/2
2: \(\left(\dfrac{1}{16}\right)^x=\left(\dfrac{1}{8}\right)^{36}\)
\(\Leftrightarrow\left(\dfrac{1}{2}\right)^{4x}=\left(\dfrac{1}{2}\right)^{108}\)
=>4x=108
hay x=27
3: \(\left(\dfrac{1}{81}\right)^x=\left(\dfrac{1}{27}\right)^4\)
\(\Leftrightarrow\left(\dfrac{1}{3}\right)^{4x}=\left(\dfrac{1}{3}\right)^{12}\)
=>4x=12
hay x=3
AN
2 tháng 1 2018
a, Theo đề ta có:
\(2.3^x-405=3^{x-1}\)
=> \(2.3^x-405=3^x:3\)
=> \(405=(2.3^x)-(3^x:3)\)
=>\(405=(2.3^x)-(3^x.\dfrac{1}{3})\)
=> \(405=3^x(2-\dfrac{1}{3})\)
=>\(405=3^x(\dfrac{6}{3}-\dfrac{1}{3})\)
=> \(405=3^x.\dfrac{5}{3}\)
=> \(3^x=405:\dfrac{5}{3}\)
=>\(3^x=405.\dfrac{3}{5}\)
=> \(3^x=81.3\)
=> \(3^x=243\)
=> \(3^x=3^5\)
=> x=5
Vậy:..............................
1 tháng 1 2018
a/ \(\dfrac{\left(-3\right)^x}{81}=-27\)
\(\Leftrightarrow\left(-3\right)^x=\left(-27\right).81\)
\(\Leftrightarrow\left(-3\right)^x=-2187\)
\(\Leftrightarrow\left(-3\right)^x=\left(-3\right)^7\)
\(\Leftrightarrow x=7\)
Vậy ...
b/ \(2^{x-1}=16\)
\(\Leftrightarrow2^{x-1}=2^4\)
\(\Leftrightarrow x-1=4\)
\(\Leftrightarrow x=5\)
Vậy ....
c/ \(\left(x-1\right)^2=25\)
\(\Leftrightarrow\left(x-1\right)^2=5^2=\left(-5\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)
Vậy ....
d/ \(0,2-\left|4,2-2x\right|=0\)
\(\Leftrightarrow\left|4,2-2x\right|=0,2\)
\(\Leftrightarrow\left[{}\begin{matrix}4,2-2x=0,2\\4,2-2x=-0,2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=4\\2x=4,4\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=2,2\end{matrix}\right.\)
Vậy ............
e, \(1\dfrac{2}{3}:\dfrac{x}{4}=6:0,3\)
\(\Leftrightarrow\dfrac{5}{3}.\dfrac{4}{x}=20\)
\(\Leftrightarrow3x=1\)
\(\Leftrightarrow x=\dfrac{1}{3}\)
Vậy ..
CN
1 tháng 1 2018
a) \(\dfrac{\left(-3\right)^x}{81}=-27\)
⇔ \(\dfrac{\left(-3\right)^x}{81}=\dfrac{-2187}{81}\)
⇔ (-3)x = -2187
⇔ (-3)x = (-3)7
⇔ x = 7
b) 2x-1 = 16
⇔ 2x-1 = 24
⇔ x - 1 = 4
⇔ x = 4 + 1
⇔ x = 5
c) (x - 1)2 = 25
⇔ \(\left[{}\begin{matrix}\left(x-1\right)^2=5^2\\\left(x-1\right)^2=\left(-5\right)^2\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}x=5+1\\x=-5+1\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)
d) 0,2 - |4,2 - 2x| = 0
⇔ |4,2 - 2x| = 0,2
⇔ \(\left[{}\begin{matrix}4,2-2x=0,2\\4,2-2x=-0,2\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}2x=4,2-0,2\\2x=4,2-\left(-0,2\right)\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}2x=4\\2x=4,4\end{matrix}\right.\)
⇔ \(\left[{}\begin{matrix}x=2\\x=2,2\end{matrix}\right.\)
e) \(1\dfrac{2}{3}:\dfrac{x}{4}=6:0,3\)
⇔ \(\dfrac{5}{3}.\dfrac{4}{x}=20\)
⇔ \(\dfrac{20}{3x}=20\)
⇔ 3x = 1
⇔ x = \(\dfrac{1}{3}\)
25 tháng 10 2018
a) \(\dfrac{x}{12}-\dfrac{5}{6}=\dfrac{1}{12}\Rightarrow\dfrac{x}{12}=\dfrac{1}{12}+\dfrac{10}{12}\Rightarrow\dfrac{x}{12}=\dfrac{11}{12}\Rightarrow x=11\)
b) \(\dfrac{2}{3}-1\dfrac{4}{15}x=\dfrac{-3}{5}\Rightarrow\dfrac{10}{15}-\dfrac{19}{15}x=\dfrac{-3}{5}\Rightarrow\dfrac{-19}{15}x=\dfrac{-13}{15}\Rightarrow x=\dfrac{13}{19}\)
c) \(\dfrac{\left(-3\right)^x}{81}=-27\Rightarrow\left(-3\right)^x=-2187\Rightarrow x=7\)
d) \(2^{x-1}=16\Rightarrow x-1=4\Rightarrow x=5\)
e) \(\left(x-1\right)^2=25\Rightarrow x-1=5\Rightarrow x=6\)
g) \(\left(3x-\dfrac{1}{4}\right)\left(x+\dfrac{1}{2}\right)=0\Rightarrow\left[{}\begin{matrix}3x-\dfrac{1}{4}=0\Rightarrow x=\dfrac{1}{12}\\x+\dfrac{1}{2}=0\Rightarrow x=\dfrac{-1}{2}\end{matrix}\right.\)
14 tháng 5 2022
a: Đặt A=0
=>-2/3x=5/9
hay x=-5/6
b: Đặt B(x)=0
=>(x-2/5)(x+2/5)=0
=>x=2/5 hoặc x=-2/5
c: Đặt C(X)=0
\(\Leftrightarrow x^3\cdot\dfrac{1}{2}=-\dfrac{4}{27}\)
\(\Leftrightarrow x^3=-\dfrac{8}{27}\)
hay x=-2/3
NH
2
28 tháng 11 2018
Mình cũng không rõ :) , nhưng tại cái đề thầy mình cho Kết quả là 7
9 tháng 9 2017
a/ \(27^x.9^x=9^{27}:81\)
\(\Leftrightarrow3^{3x}.3^{2x}=3^{54}:3^4\)
\(\Leftrightarrow3^{2x+3x}=3^{50}\)
\(\Leftrightarrow2x+3x=50\)
\(\Leftrightarrow5x=50\)
\(\Leftrightarrow x=10\)
Vậy ...
C
9 tháng 9 2017
\(a.27^x.9^x=9^{27}:81\)
\(\left(3^3\right)^x.\left(3^2\right)^x=\left(3^2\right)^{27}:\left(3^2\right)^2\)
\(3^{3x}.3^{2x}=3^{50}\)
\(3^{3x+2x}=3^{50}\)
\(\Rightarrow3x+2x=50\)
\(x\left(3+2\right)=50\)
\(x=50:5=10\)
Vậy\(x=10\)
\(b.\left(\dfrac{12}{25}\right)^x=\left(\dfrac{5}{3}\right)^{-2}-\left(-\dfrac{3}{5}\right)^4\)
\(\left(\dfrac{12}{25}\right)^x=\dfrac{9}{25}-\dfrac{81}{625}\)
\(\left(\dfrac{12}{25}\right)^x=\dfrac{144}{625}\)( Đề sai )
PN
7 tháng 1 2018
1.
\(\left(\dfrac{-2}{3}\right).0,75+1\dfrac{2}{3}:\left(\dfrac{-4}{9}\right)+\left(\dfrac{-1}{2}\right)^2\)
\(=\left(\dfrac{-2}{3}\right).\dfrac{3}{4}+\dfrac{5}{3}.\left(\dfrac{9}{-4}\right)+\dfrac{1}{4}\)
\(=-\dfrac{1}{2}+\dfrac{45}{-12}+\dfrac{1}{4}\)
\(=-\dfrac{6}{12}+\dfrac{-45}{12}+\dfrac{3}{4}\)
\(=\dfrac{-48}{12}\)
\(=-4\)
2.
a) \(\dfrac{3}{4}-\left(x+\dfrac{1}{2}\right)=\dfrac{4}{5}\)
\(\Leftrightarrow x+\dfrac{1}{2}=\dfrac{3}{4}-\dfrac{4}{5}\)
\(\Leftrightarrow x+\dfrac{1}{2}=\dfrac{-1}{20}\)
\(\Leftrightarrow x=\dfrac{-1}{20}-\dfrac{1}{2}\)
\(\Leftrightarrow x=\dfrac{-1}{20}-\dfrac{10}{20}\)
\(\Leftrightarrow x=\dfrac{-11}{20}\)
b) \(\left|x-\dfrac{2}{5}\right|+\dfrac{3}{4}=\dfrac{11}{4}\)
\(\Leftrightarrow\left|x-\dfrac{2}{5}\right|=\dfrac{11}{4}-\dfrac{3}{4}\)
\(\Leftrightarrow\left|x-\dfrac{2}{5}\right|=2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{2}{5}=-2\Rightarrow x=-2+\dfrac{2}{5}=\dfrac{-8}{5}\\x-\dfrac{2}{5}=2\Rightarrow x=2+\dfrac{2}{5}=\dfrac{12}{5}\end{matrix}\right.\)
3.
a) \(\dfrac{16}{2^n}=2\)
\(\Leftrightarrow2^n=16:2\)
\(\Leftrightarrow2^n=8\)
\(\Leftrightarrow2^n=2^3\)
\(\Leftrightarrow n=3\)
b) \(\dfrac{\left(-3\right)^n}{81}=-27\)
\(\Leftrightarrow\left(-3\right)^n=\left(-27\right).81\)
\(\Leftrightarrow\left(-3\right)^n=\left(-3\right)^3.\left(-3\right)^4\)
\(\Leftrightarrow\left(-3\right)^n=\left(-3\right)^7\)
\(\Leftrightarrow n=7\)
4. Ta có:
\(\dfrac{x}{2}=\dfrac{y}{3}\Rightarrow\dfrac{x}{10}=\dfrac{y}{15}\) (1)
\(\dfrac{y}{5}=\dfrac{z}{4}\Rightarrow\dfrac{y}{15}=\dfrac{z}{12}\) (2)
Từ (1) và (2) suy ra \(\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}\)
Vì \(x-y+x=-49\) ta có:
\(\dfrac{x}{10}=\dfrac{y}{15}=\dfrac{z}{12}=\dfrac{x-y+z}{10-15+12}=\dfrac{-49}{7}=-7\)
Vậy \(\left\{{}\begin{matrix}x=\left(-7\right).10=-70\\y=\left(-7\right).15=-105\\z=\left(-7\right).12=-84\end{matrix}\right.\)
HD
17 tháng 10 2017
\(a)\left(\dfrac{-2}{3}\right)^2.x=\left(\dfrac{-2}{3}\right)^5\)
\(\Rightarrow x=\left(\dfrac{-2}{3}\right)^5:\left(\dfrac{-2}{3}\right)^2\)
\(\Rightarrow x=\left(\dfrac{-2}{3}\right)^3\)
Vậy ...............
\(b)\left(-\dfrac{1}{3}\right)^3.x=\dfrac{1}{81}\)
\(\Rightarrow\dfrac{-1}{27}.x=\dfrac{1}{81}\)
\(\Rightarrow x=\dfrac{1}{81}:\dfrac{-1}{27}\)
\(\Rightarrow x=\dfrac{-1}{3}\)
Vậy ..................
Chúc bạn học tốt!
\(\Leftrightarrow\dfrac{\left(-3\right)^x}{3^4}=\left(-3\right)^3\\ \Leftrightarrow\left(-3\right)^x=\left(-3\right)^3\cdot\left(-3\right)^4=\left(-3\right)^7\\ \Leftrightarrow x=7\)