Tìm x
c) 4-x = 2(x-4)^2
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XL
3
31 tháng 1 2022
Bài 4:
a) \(\dfrac{x}{2}=\dfrac{2}{4}\)
\(\Rightarrow\dfrac{x}{2}=\dfrac{1}{2}\)
\(\Rightarrow x=2\)
Vậy: \(x=2\)
b) \(-\dfrac{1}{5}=\dfrac{2}{x}\)
\(\Rightarrow x=\dfrac{-5.2}{1}=-10\)
Vậy: \(x=-10\)
c) \(\dfrac{x}{5}=\dfrac{5}{x}\)
\(\Rightarrow x^2=25\)
\(\Rightarrow\left[{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\)
Vậy: \(x\in\left\{5;-5\right\}\)
TH
2
19 tháng 7 2021
Giải:
a) \(2^5=4^x\)
\(\Rightarrow2^5=\left(2^2\right)^x\)
\(\Rightarrow2^5=2^{2x}\)
\(\Rightarrow2x=5\)
\(\Rightarrow x=\dfrac{5}{2}\)
b) \(2.4^2.8^3.16^4=8^x\)
\(\Rightarrow2.\left(2^2\right)^2.\left(2^3\right)^3.\left(2^4\right)^4=\left(2^3\right)^x\)
\(\Rightarrow2.2^4.2^9.2^{16}=2^{3x}\)
\(\Rightarrow2^{30}=2^{3x}\)
\(\Rightarrow3x=30\)
\(\Rightarrow x=30:3\)
\(\Rightarrow x=10\)
c) \(3^3:3^5=9^x\)
\(\Rightarrow3^{-2}=\left(3^2\right)^x\)
\(\Rightarrow3^{-2}=3^{2x}\)
\(\Rightarrow2x=-2\)
\(\Rightarrow x=-2:2\)
\(\Rightarrow x=-1\)
Chúc bạn học tốt!
19 tháng 7 2021
a) Ta có: \(2^5=4^x\)
nên \(2^{2x}=2^5\)
\(\Leftrightarrow2x=5\)
hay \(x=\dfrac{5}{2}\)
b) Ta có: \(2\cdot4^2\cdot8^3\cdot16^4=8^x\)
\(\Leftrightarrow2^{3x}=2\cdot2^5\cdot2^9\cdot2^{16}=2^{31}\)
\(\Leftrightarrow3x=31\)
hay \(x=\dfrac{31}{3}\)
c) Ta có: \(3^3:3^5=9^x\)
\(\Leftrightarrow3^{-2}=3^{2x}\)
\(\Leftrightarrow2x=-2\)
hay x=-1
22 tháng 6 2023
a: =>1/3x-2/5x=5
=>-1/15x=5
=>x=-75
b: =>4x=4
=>x=1
c: =>6*3^x-5*3^x=243
=>3^x=243
=>x=5
3 tháng 2 2021
a) Ta có: \(3\left(2-x\right)+1=4-2x\)
\(\Leftrightarrow6-3x+1-4+2x=0\)
\(\Leftrightarrow-x+3=0\)
\(\Leftrightarrow-x=-3\)
hay x=3
Vậy: S={3}
b) Ta có: \(2\left(x+4\right)=3-x\)
\(\Leftrightarrow2x+8-3+x=0\)
\(\Leftrightarrow3x+5=0\)
\(\Leftrightarrow3x=-5\)
hay \(x=-\dfrac{5}{3}\)
Vậy: \(S=\left\{-\dfrac{5}{3}\right\}\)
c) Ta có: \(7-3x=x-5\)
\(\Leftrightarrow7-3x-x+5=0\)
\(\Leftrightarrow-4x+12=0\)
\(\Leftrightarrow-4x=-12\)
hay x=3
Vậy: S={3}
d) Ta có: \(5x-\left(x-1\right)=7\)
\(\Leftrightarrow5x-x+1=7\)
\(\Leftrightarrow4x=6\)
hay \(x=\dfrac{3}{2}\)
Vậy: \(S=\left\{\dfrac{3}{2}\right\}\)
22 tháng 8 2021
a, \(\left(x+2\right)\left(x+4\right)-x^2=24\\ \Rightarrow x^2+6x+8-x^2=24\\ \Rightarrow6x+8=24\\ \Rightarrow6x=16\\ \Rightarrow x=\dfrac{8}{3}\)
b, \(\left(x+5\right)\left(x-5\right)=x^2+x\)
\(\Rightarrow x^2+x-\left(x+5\right)\left(x-5\right)=0\)
\(\Rightarrow x^2+x-x^2+25=0\\ \Rightarrow x+25=0\\ \Rightarrow x=-25\)
22 tháng 8 2021
\(a,< =>x^2+4x+2x+8-x^2=24< =>6x+8=24< =>x=\dfrac{24-8}{6}=\dfrac{8}{3}\)
b,\(< =>x^2-25-x^2-x=0< =>-25-x=0< =>x=-25\)
c,\(< =>4x^2-9-4x^2+4x=0< =>4x-9=0< =>x=\dfrac{9}{4}\)
d,\(< =>x^3+2^3=9< =>x^3=1=>x=1\)
17 tháng 1 2022
\(a,\dfrac{6}{5}=\dfrac{18}{x}\\ \Rightarrow x=18:\dfrac{6}{5}\\ \Rightarrow x=15\\ b,\dfrac{3}{4}=\dfrac{-21}{x}\\ \Rightarrow x=-21:\dfrac{3}{4}\\ \Rightarrow x=-28\\ c,\dfrac{2}{-7}=\dfrac{18}{x}\\ \Rightarrow x=18:\dfrac{2}{-7}\\ \Rightarrow x=-63\\ d,\dfrac{-5}{2}=\dfrac{10}{-x}\\ \Rightarrow x=-10:\dfrac{-5}{2}\\ \Rightarrow x=4\)
NA
17 tháng 1 2022
\(a,\dfrac{6}{5}=\dfrac{18}{x}\Rightarrow6.x=5.18=90\\ \Rightarrow6.x=90\\ \Rightarrow x=15\\ b,\dfrac{3}{4}=\dfrac{-21}{x}\Rightarrow3.x=4.21=84\\ \Rightarrow x=28\)
H9
HT.Phong (9A5)
CTVHS
9 tháng 7 2023
c) \(\left(34-2x\right)\left(2x-6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}34-2x=0\\2x-6-0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x=34\\2x=6\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=17\\x=3\end{matrix}\right.\)
d) \(\left(2019-x\right)\left(3x-12\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}2019-x=0\\3x-12=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=2019\\3x=12\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=2019\\x=4\end{matrix}\right.\)
e) \(57\left(9x-27\right)=0\)
\(\Rightarrow9x-27=0\)
\(\Rightarrow9\left(x-3\right)=0\)
\(\Rightarrow x-3=0\)
\(\Rightarrow x=3\)
f) \(25+\left(15-x\right)=30\)
\(\Rightarrow25+15-x=30\)
\(\Rightarrow40-x=30\)
\(\Rightarrow x=40-30\)
\(\Rightarrow x=10\)
g) \(43-\left(24-x\right)=20\)
\(\Rightarrow43-24+x=20\)
\(\Rightarrow19+x=20\)
\(\Rightarrow x=20-19\)
\(\Rightarrow x=1\)
h) \(2\left(x-5\right)-17=25\)
\(\Rightarrow2\left(x-5\right)=17+25\)
\(\Rightarrow x-5=21\)
\(\Rightarrow x=21+5\)
\(\Rightarrow x=26\)
i) \(3\left(x+7\right)-15=27\)
\(\Rightarrow3\left(x+7\right)=27+15\)
\(\Rightarrow x+7=14\)
\(\Rightarrow x=14-7\)
\(\Rightarrow x=7\)
j) \(15+4\left(x-2\right)=95\)
\(\Rightarrow4\left(x-2\right)=95-15\)
\(\Rightarrow4\left(x-2\right)=80\)
\(\Rightarrow x-2=20\)
\(\Rightarrow x=20+2\)
\(\Rightarrow x=22\)
k) \(20-\left(x+14\right)=5\)
\(\Rightarrow x+14=20-5\)
\(\Rightarrow x+14=15\)
\(\Rightarrow x=15-14\)
\(\Rightarrow x=1\)
l) \(14+3\left(5-x\right)=27\)
\(\Rightarrow3\left(5-x\right)=27-14\)
\(\Rightarrow3\left(5-x\right)=13\)
\(\Rightarrow5-x=\dfrac{13}{3}\)
\(\Rightarrow x=5-\dfrac{13}{3}\)
\(\Rightarrow x=\dfrac{2}{3}\)
\(4-x=2\left(x-4\right)^2\)
\(\Rightarrow4-x=2x^2-16x+32\)
\(\Rightarrow2x^2-15x+28=0\)
\(\Rightarrow2x\left(x-4\right)-7\left(x-4\right)=0\)
\(\Rightarrow\left(x-4\right)\left(2x-7\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=4\\x=\dfrac{7}{2}\end{matrix}\right.\)