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12 tháng 7 2019
a) \(\frac{x}{x+1}=\frac{1}{2}\)
=> 2x = x + 1
=> 2x - x = 1
=> x = 1
b) \(\frac{x}{2}=\frac{x}{3}\)
=> 3x = 2x
=> 3x - 2x = 0
=> x = 0
c) \(\frac{x+1}{2}=\frac{x+1}{2017}\)
=> \(2017\left(x+1\right)=2\left(x+1\right)\)
=> 2017x + 2017 = 2x + 2
=> 2017x - 2x = 2 - 2017
=> 2015x = -2015
=> x = -2015 : 2015
=> x = -1
i) \(\frac{3}{x}=\frac{x}{2017}\)
=> x2 = 2017.3
=> x2 = 6051
=> \(\orbr{\begin{cases}x=\sqrt{6051}\\x=-\sqrt{6051}\end{cases}}\)
còn lại tự lm
12 tháng 7 2019
\(a,\frac{x}{x+1}=\frac{1}{2}\)
\(\Rightarrow x=\frac{1}{2}.\left(x+1\right)\)
\(\Rightarrow x=\frac{1}{2}x+\frac{1}{2}\)
\(\Rightarrow x-\frac{1}{2}x=\frac{1}{2}\)
\(\Rightarrow\frac{1}{2}x=\frac{1}{2}\)
\(\Rightarrow x=1\)
\(b,\frac{x}{2}=\frac{x}{3}\)
\(\Rightarrow x=\frac{x}{3}.2\)
\(\Rightarrow x=\frac{2x}{3}\)
\(\Rightarrow3x=2x\)
\(\Rightarrow x=0\)
\(c,\frac{x+1}{2}=\frac{x+1}{2017}\)
\(\Rightarrow x+1=\frac{x+1}{2017}.2\)
\(\Rightarrow x+1=\frac{2x+2}{2017}\)
\(\Rightarrow2017x+2017=2x+2\)
\(\Rightarrow2017x-2x=2-2017\)
\(\Rightarrow2015x=-2015\)
\(\Rightarrow x=-1\)
\(i,\frac{3}{x}=\frac{x}{2017}\)
\(\Rightarrow x=3:\frac{x}{2017}\)
\(\Rightarrow x=\frac{6051}{x}\)
\(\Rightarrow x^2=6051\)
\(\Rightarrow x=\sqrt{6051}\)
\(o,\frac{x}{3}=\frac{x+1}{2}\)
\(\Rightarrow x=\frac{x+1}{2}.3\)
\(\Rightarrow x=\frac{3x+3}{2}\)
\(\Rightarrow2x=3x+3\)
\(\Rightarrow-x=3\)
\(\Rightarrow x=-3\)
\(m,\frac{x+1}{2}=\frac{x+2}{3}\)
\(\Rightarrow x+1=\frac{x+2}{3}.2\)
\(\Rightarrow x+1=\frac{2x+4}{3}\)
\(\Rightarrow3x+3=2x+4\)
\(\Rightarrow x=1\)
\(p,\frac{x+1}{2}=x\)
\(\Rightarrow2x=x+1\)
\(\Rightarrow x=1\)
\(m,\frac{2}{x}=\frac{x}{8}\)
\(\Rightarrow x=2:\frac{x}{8}\)
\(\Rightarrow x=\frac{16}{x}\)
\(\Rightarrow x^2=16\)
\(\Rightarrow x=4\)
\(Q,\frac{x^2}{2}=\frac{8}{x^2}\)
\(\Rightarrow x^2=\frac{8}{x^2}.2\)
\(\Rightarrow x^2=\frac{16}{x^2}\)
\(\Rightarrow x^4=16\)
\(\Rightarrow x=2\)
\(r,\frac{x^3}{2}=\frac{32}{x}\)
\(\Rightarrow x^3=\frac{32}{x}.2\)
\(\Rightarrow x^3=\frac{64}{x}\)
\(\Rightarrow x^4=64\)
\(\Rightarrow x=\sqrt[4]{64}\)
XU
5 tháng 1 2020
a, 2x(x-1) - 3x(x+1)
= 2x2 - 2x - 3x2 - 3x
= -x2 - 5x
b, (x-1)(x+2) - (x-2)(x+1)
= x2 + 2x - x - 2 - x2 - x + 2x + 2
= 2x
c, (x-1)2 - (x+2)2
= x2 - 2x + 1 - x2 - 4x + 4
= -6x + 5
d, (2x-1)(2x-1) - 4(x+1)2
= 4x2 - 2x - 2x + 1 - 4(x2 + 2x + 1)
= 4x2 - 2x - 2x + 1 - 4x2 - 8x - 4
= -12x - 3
Chúc bạn học tốt! 
KL
5 tháng 1 2020
a) 2x . (x-1) - 3x . (x+1)
= 2x2 - 2x - 3x2 - 3x
= - x2 - 5x
= - x (x +5)
b) (x - 1) . (x + 2) - (x - 2) . (x + 1)
= x2 + 2x - x - 2 - x2 + x - 2x - 2
= - 4
c) (x - 1)2 - (x + 2)2
= (x - 1 -x -2) (x + 1 + x + 2)
= - 3 (2x + 3)
d) (2x - 1) . (2x - 1) - 4 (x + 1)2
=
22 tháng 6 2017
1, \(\left(2x+3\right)^2-\left(2x+1\right)\left(2x-1\right)=5\)
\(\Leftrightarrow4x^2+12x+9-4x^2-1=5\)
\(\Leftrightarrow12x=-3\)
\(\Leftrightarrow x=\dfrac{-1}{4}\)
Vậy \(x=\dfrac{-1}{4}\)
2, \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x^2+5\right)=20\)
\(\Leftrightarrow x^3+27-x^3-5x=20\)
\(\Leftrightarrow5x=7\)
\(\Leftrightarrow x=\dfrac{7}{5}\)
Vậy...
5, \(x^2-9+5\left(x+3\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x+3\right)+5\left(x+3\right)=0\)
\(\Leftrightarrow\left(x+3\right)\left(x-3+5\right)=0\)
\(\Leftrightarrow\left(x+3\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+3=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-2\end{matrix}\right.\)
Vậy...
Q
22 tháng 6 2017
1) \(\left(2x+3\right)^2-\left(2x+1\right)\left(2x-1\right)=5\) (1)
\(\Leftrightarrow4x^2+12x+9-\left(4x^2-1\right)=5\)
\(\Leftrightarrow4x^2+12x+9-4x^2+1=5\)
\(\Leftrightarrow12x+10=5\)
\(\Leftrightarrow12x=5-10\)
\(\Leftrightarrow12x=-5\)
\(\Leftrightarrow x=-\dfrac{5}{12}\)
Vậy tập nghiệm phương trình (1) là \(S=\left\{-\dfrac{5}{12}\right\}\)
2) \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x^2+5\right)=20\) (2)
\(\Leftrightarrow x^3+27-x^3-5x=20\)
\(\Leftrightarrow27-5x=20\)
\(\Leftrightarrow-5x=20-27\)
\(\Leftrightarrow-5x=-7\)
\(\Leftrightarrow x=\dfrac{7}{5}\)
Vậy tập nghiệm phương trình (2) là \(S=\left\{\dfrac{7}{5}\right\}\)
3) \(\left(x+2\right)^3-x\left(x^2+6x\right)=15\) (3)
\(\Leftrightarrow x^3+6x^2+12x+8-x^3-6x^2=15\)
\(\Leftrightarrow12x+8=15\)
\(\Leftrightarrow12x=15-8\)
\(\Leftrightarrow12x=7\)
\(\Leftrightarrow x=\dfrac{7}{12}\)
Vậy tập nghiệm phương trình (3) là \(S=\left\{\dfrac{7}{12}\right\}\)
4) \(\left(x-1\right)\left(x^2+x+1\right)-x\left(x+10\right)\left(x-1\right)=7\) (4)
\(\Leftrightarrow\left(x-1\right)\left(x^2+x+1-x\left(x+10\right)\right)=7\)
\(\Leftrightarrow\left(x-1\right)\left(x^2+x+1-x^2-10x\right)=7\)
\(\Leftrightarrow\left(x-1\right)\left(-9x+1\right)=7\)
\(\Leftrightarrow-9x^2+x+9x-1=7\)
\(\Leftrightarrow-9x^2+10-1=7\)
\(\Leftrightarrow-9x^2+10x-1-7=0\)
\(\Leftrightarrow-9x^2+10x-8=0\)
\(\Leftrightarrow9x^2-10x+8=0\)
\(\Leftrightarrow x\notin R\)
5) \(x^2-9+5\left(x+3\right)=0\) (5)
\(\Leftrightarrow x^2-9+5x+15=0\)
\(\Leftrightarrow x^2+5x+6=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-5+1}{2}\\x=\dfrac{-5-1}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=-3\end{matrix}\right.\)
Vậy tập nghiệm phương trình (5) là \(S=\left\{-3;-2\right\}\)
DH
6 tháng 7 2017
a, \(3\left(1-4x\right)\left(x-1\right)+4\left(3x-2\right)\left(x+3\right)=-27\)
\(\Rightarrow3\left(x-1-4x^2+4x\right)+4\left(3x^2+9x-2x-6\right)=-27\)
\(\Rightarrow15x-3-12x^2+12x^2+28x-24=-27\)
\(\Rightarrow43x=-27+24+3\Rightarrow x=0\)
Các câu còn lại làm tương tự! Phá tan tành hoa loa kèn nhà nó ra!
Chúc bạn học tốt!!!
HT
3 tháng 8 2021
4, Q = |x+\(\frac{1}{5}\) | -x +\(\frac{4}{7}\)
xét x \(\ge\) \(-\frac{1}{5}\)
Ta Có Q = |x+\(\frac{1}{5}\) | -x + \(\frac{4}{7}\) = x+\(\frac{1}{5}\) - x +\(\frac{4}{7}\) = \(\frac{27}{35}\) (1)
xét x \(< -\frac{1}{5}\)
Ta có Q = | x +\(\frac{1}{5}\) | - x + \(\frac{4}{7}\) = -x - \(\frac{1}{5}\) - x + \(\frac{4}{7}\) = -2x + \(\frac{13}{35}\)
với x \(< -\frac{1}{5}\)
=> -2x \(>\) \(\frac{2}{5}\)
=> -2x + \(\frac{13}{35}\) \(>\frac{27}{35}\) (2)
Từ (1) và (2) => MinQ = \(\frac{27}{35}\) khi \(x\ge-\frac{1}{5}\)
5 , D = |x| + |8-x|
D = |x| + |8-x| \(\ge\) |x+8-x| = |8| = 8
Dấu ''='' xảy ra khi x(8-x) \(\ge\) 0 <=> 0\(\le\)x\(\le\) 8
Vậy MinD = 8 khi \(0\le x\le8\)
6,L= |x - 2012| + |2011 - x|
L = |x-2012| + |2011-x| \(\ge\) | x-2012 + 2011 - x | = |-1| = 1
Dấu ''= '' xảy ra khi ( x-2012)(2011-x) \(\ge\) 0
HT
3 tháng 8 2021
làm nốt câu 6 nãy ấn nhầm
<=> 2011\(\le\) x \(\le\) 2012
Vậy MinL = 1 khi \(2011\le x\le2012\)
7 , E = | x- \(\frac{2006}{2007}\) | + |x-1|
Ta có :
E = |x-\(\frac{2006}{2007}\) | + |1-x|
E = | x - \(\frac{2006}{2007}\) | + |1-x| \(\ge\) | x - \(\frac{2006}{2007}\) + 1 - x | = \(\frac{1}{2007}\)
Dấu ''='' xảy ra khi (x- \(\frac{2006}{2007}\) ) ( 1-x ) \(\ge0\) <=> \(\frac{2006}{2007}\le x\le1\)
Vậy MinE = \(\frac{1}{2007}\) khi \(\frac{2006}{2007}\le x\le1\)
8 ,F = | x -\(\frac{1}{4}\) | + | \(x-\frac{3}{4}\) |
Ta có :
F = | x - \(\frac{1}{4}\) | + | \(\frac{3}{4}\) - x |
F = | x - \(\frac{1}{4}\) | + | \(\frac{3}{4}\) -x | \(\ge\) | x - \(\frac{1}{4}\) + \(\frac{3}{4}\) -x | = \(\frac{1}{2}\)
Dấu ''='' xảy ra khi ( x-\(\frac{1}{4}\) ) ( \(\frac{3}{4}-x\) ) \(\ge\) 0 <=> \(\frac{1}{4}\le x\le\frac{3}{4}\)
Vậy MinF = \(\frac{1}{2}\) khi \(\frac{1}{4}\le x\le\frac{3}{4}\)
6 tháng 8 2022
a: =>(3/2-2x):2/3=1/6
=>3/2-2x=1/6x2/3=2/18=1/9
=>2x=25/18
hay x=25/36
b: \(\Leftrightarrow2x-2x+\dfrac{5}{2}-2=x-\dfrac{1}{4}\)
=>x-1/4=1/2
=>x=3/4
c: \(\Leftrightarrow2x-\dfrac{2}{3}-\dfrac{1}{3}x+\dfrac{1}{4}x=0\)
=>23/12x=2/3
=>x=8/23
NT
1
12 tháng 7 2018
\(4\left(x-1\right)-2\left(x-2\right)=3\)
\(\Leftrightarrow\) \(4x-4-2x+4=3\)
\(\Leftrightarrow\) \(2x=4\)
(\(x\) - 1) = 2 - \(x\)
\(x-1\) = 2 - \(x\)
\(x+x\) = 2 + 1
2\(x\) = 3
\(x=\dfrac{3}{2}\)
Vậy \(x=\dfrac{3}{2}\)