Решить неравенство [latex]\log_{x^2-x+1}(x^2+6x+8)+\log_{\frac{1}{x^2-x+1}}(x+2)\ \textless \ \frac{1}{\log_{5/2}(x^2-x+1)}[/latex]
Решить неравенство
[latex]\log_{x^2-x+1}(x^2+6x+8)+\log_{\frac{1}{x^2-x+1}}(x+2)\ \textless \ \frac{1}{\log_{5/2}(x^2-x+1)}[/latex]
Ответ(ы) на вопрос:
Гость
[latex] \log_{x^2-x+1}(x^2+6x+8)+\log_{\frac{1}{x^2-x+1}}(x+2)\ \textless \ \frac{1}{\log_{ \frac{5}{2} }(x^2-x+1)}[/latex]
Найдем ОДЗ:
[latex]1) [/latex]
[latex]x^2-x+1 \neq 1} [/latex]
[latex]{{x^2-x \neq 0} [/latex]
[latex]x(x-1) \neq 0[/latex]
[latex]x \neq 0,[/latex] [latex]x \neq 1[/latex]
[latex]2)[/latex]
[latex] x^{2} -x+1\ \textgreater \ 0[/latex]
[latex] x^{2} -x+1=0[/latex]
[latex]D=(-1)^2-4*1*1\ \textless \ 0[/latex]
[latex]a=1\ \textgreater \ 0[/latex]
парабола [latex]y=x^2-x+1[/latex] расположена над осью OX, т. е. [latex]y\ \textgreater \ 0[/latex] при любом значении x, поэтому данное неравенство верно при любых значениях x, т. е. [latex]x[/latex] ∈ [latex]R[/latex]
[latex]3)[/latex]
[latex] x^{2} +6x+8\ \textgreater \ 0[/latex]
[latex]x^2+6x+8=0[/latex]
[latex]D=6^2-4*1*8=4[/latex]
[latex]x_1= \frac{-6+2}{2} =-2[/latex]
[latex]x_2= \frac{-6-2}{2} =-4[/latex]
[latex](x+2)(x+4)\ \textgreater \ 0[/latex]
[latex]4) [/latex]
[latex]log_{2.5}(x^2-x+1) \neq 0[/latex]
[latex]log_{2.5}(x^2-x+1) \neq log_{2.5}1[/latex]
[latex]x^2-x+1 \neq 1[/latex]
[latex]x \neq 0,[/latex] [latex]x \neq 1[/latex]
[latex]5)[/latex]
[latex]x+2\ \textgreater \ 0[/latex]
[latex]x\ \textgreater \ -2[/latex]
Отметим на числовой прямой и найдем общее решение ОДЗ:
+ - +
----------(-4)---------------(-2)-------------------
////////////// /////////////////
------------------------------------(0)-----(1)---------
/////////////////////////////////////////////////////////
-------------------------------(-2)---------------------
/////////////////
[latex]x[/latex] ∈ [latex](-2;0)[/latex] ∪ [latex](0;1)[/latex] ∪ [latex](1;+[/latex] ∞ [latex])[/latex]
[latex]\log_{x^2-x+1}(x^2+6x+8)+\log_{{(x^2-x+1)^{-1}}}(x+2)\ \textless \ {\log_{x^2-x+1}2.5}[/latex]
[latex]\log_{x^2-x+1}(x^2+6x+8)-\log_{{x^2-x+1}}(x+2)\ \textless \ {\log_{x^2-x+1}2.5}[/latex]
[latex]\log_{x^2-x+1}(x^2+6x+8)\ \textless \ {\log_{x^2-x+1}2.5}+\log_{{x^2-x+1}}(x+2)[/latex]
[latex]\log_{x^2-x+1}(x^2+6x+8)\ \textless \ {\log_{x^2-x+1}[2.5(x+2)]}[/latex]
[latex]\log_{x^2-x+1}(x^2+6x+8)\ \textless \ {\log_{x^2-x+1}(2.5x+5)}[/latex]
[latex]1)[/latex]
[latex] \left \{ {{0\ \textless \ x^2-x+1\ \textless \ 1} \atop {x^2+6x+8\ \textgreater \ 2.5x+5}}} \right. [/latex]
[latex] \left \{ {{x^2-x+1\ \textgreater \ 0}\atop {x^2-x+1\ \textless \ 1}} \atop {x^2+6x+8\ \textgreater \ 2.5x+5}}} \right. [/latex]
[latex] \left \{ {{x^2-x+1\ \textgreater \ 0}\atop {x^2-x\ \textless \ 0}} \atop {x^2+3.5x+3\ \textgreater \ 0}}} \right. [/latex]
[latex] \left \{ {{x^2-x+1\ \textgreater \ 0}\atop {x(x-1)\ \textless \ 0}} \atop {x^2+3.5x+3\ \textgreater \ 0}}} \right. [/latex]
[latex] x^{2} +3.5x+3=0[/latex]
[latex]D=3.5^2-4*1*3=12.25-12=0.25[/latex]
[latex]x_1= \frac{-3.5+0.5}{2}=-1.5 [/latex]
[latex]x_2= \frac{-3.5-0.5}{2}=-2[/latex]
[latex] x^{2} -x+1\ \textgreater \ 0[/latex] ⇒ [latex]x[/latex] ∈ [latex]R[/latex]
+ - +
-------------------------(0)-------(1)-------------
///////////
+ - +
-----(-2)-----(-1.5)-------------------------------
//////// //////////////////////////////
[latex]x[/latex] ∈ [latex](0;1)[/latex]
[latex]2)[/latex]
[latex]\left \{ {{x^2-x+1\ \textgreater \ 1} \atop {x^2+6x+8\ \textless \ 2.5x+5}}} \right.[/latex]
[latex]\left \{ {{x^2-x\ \textgreater \ 0} \atop {x^2+3.5x+3\ \textless \ 0}}} \right.[/latex]
[latex]\left \{ {{x(x-1)\ \textgreater \ 0} \atop {(x+1.5)(x+2)\ \textless \ 0}}} \right.[/latex]
+ - +
-----------------------------(0)-------------(1)--------------
/////////////////////////////////// //////////////
+ - +
---------(-2)-------(-1.5)------------------------------
//////////
[latex]x[/latex] ∈ [latex](-2;-1.5)[/latex]
Объединяем 1) и 2) случаи и получаем общее решение неравенства:
[latex]x[/latex] ∈ [latex](-2;-1.5)[/latex] ∪ [latex](0;1)[/latex]
Найдем пересечение с ОДЗ:
-------------------------(-2)--------------(0)-----(1)-----------------
/////////////////////////////////////////////
--------------------------(-2)---(-1.5)----(0)-----(1)----------------
/////// ////////
Ответ: [latex](-2;-1.5)[/latex] ∪ [latex](0;1)[/latex]
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