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how do i solve: ^2log(-2x+3) - ^2log(x+1)>0

 Mar 22, 2016
 #1
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how do i solve: ^2log(-2x+3) - ^2log(x+1)>0

 

-1<x<2/3

 Mar 22, 2016
 #2
avatar+26388 
+5

how do i solve: ^2log(-2x+3) - ^2log(x+1)>0

 

rearrange:

\(\begin{array}{rcll} ^2log(-2x+3) - ^2log(x+1) &>& 0 \\ \log_{2}{ (-2x+3) } -\log_{2}{ (x+1) }&>& 0 \\ \log_{2}{ \left( \frac{-2x+3}{x+1} \right) } &>& 0 \quad & | \quad 2^{()}\\ \frac{-2x+3}{x+1} & > & 2^0 \quad & | \quad 2^0 = 1\\ \frac{-2x+3}{x+1} & > & 1\\ \end{array}\)

\(\boxed{~ \begin{array}{rcll} \dfrac{-2x+3}{x+1} & > & 1 \qquad D = R ~ \backslash ~ \{-1\}\\ \end{array} ~}\)

 

\(\small{ \begin{array}{ccc|ccc} \hline \text{denominator } x+1 > 0 && & \text{denominator } x+1< 0 && \\ \\ \hline -2x+3~ >~ 1\cdot(x+1) &&& -2x+3 {\color{red}~<~} 1\cdot(x+1)&& \\ \\ \begin{array}{ccc|c} x+1 &>& 0 & -1 \\ -2x+3 &>& x+1 & +2x-1\\ \hline \end{array} &&& \begin{array}{ccc|c} x+1 &<& 0 & -1 \\ -2x+3 &<& x+1 & +2x-1\\ \hline \end{array} \\\\ \begin{array}{ccc|c} x &>& -1 & \\ 2 &>& 3x & :3\\ \hline \end{array} &&& \begin{array}{ccc|c} x &<& -1 & \\ 2 &<& 3x & :3\\ \hline \end{array} \\\\ \begin{array}{ccc|c} x &>& -1 & \\ \frac23 &>& x & \\ \hline \end{array} &&& \begin{array}{ccc|c} x &<& -1 & \\ \frac23 &<& 3x & \\ \hline \end{array} \\\\ \mathbf{ -1 < x < \frac23 }&& & \text{no solution}&& \end{array} }\)

 

laugh

 Mar 22, 2016
edited by heureka  Mar 22, 2016
edited by heureka  Mar 22, 2016
edited by heureka  Mar 22, 2016
edited by heureka  Mar 22, 2016
edited by heureka  Mar 22, 2016
 #3
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0

hello, there were still things i couldnt understand.

for example the first part of the answer were u had put in that D=R \{-1}...I would like to know how you got -1 as answer.

 

Further on i would like to know were f(x)-g(x)>0 can be found in a graphic (if this exist and is possible)

 Mar 23, 2016
 #4
avatar+26388 
0

Hallo Guest

 

The denominator must not 0 (null).

 

The denominator is 0, if

 \(\begin{array}{rcll} x+1 &=& 0 \quad & | \quad -1\\ x+1-1 &=& 0-1 \\ x+0 &=& -1 \\ x &=& -1 \end{array}\)

 

so \(x=-1\) is not permissible or \(D = R ~ \backslash ~ \{-1\}\)

 

 

 

\(\dfrac{-2x+3}{x+1} > 1\)

 

 

laugh

heureka  Mar 23, 2016
 #5
avatar+26388 
0

Hallo Guest

 

The denominator must not 0 (null).

 

The denominator is 0, if

 \(\begin{array}{rcll} x+1 &=& 0 \quad & | \quad -1\\ x+1-1 &=& 0-1 \\ x+0 &=& -1 \\ x &=& -1 \end{array}\)

 

so \(x=-1\) is not permissible or \(D = R ~ \backslash ~ \{-1\}\)

 

 

 

\(\dfrac{-2x+3}{x+1} > 1\)

 

 

 

 

laugh

heureka  Mar 23, 2016
 #6
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0

Hello,

 i see that u had put 2 solutions for the denominator in 2 different ways, but on the right side and the last part....does 3x still remain unsolved after u had divided it by 3

2 < 3x | :3

2/3 < 3x 

does the (x) still remain there? or should it look like this:

 2 < 3x | :3

2/3 < 3

 Mar 24, 2016

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