Решите неравенство (log2^2 x - 2log2 x )^2 + 36log2 x + 45 меньше 18log2^2 x
Решите неравенство (log2^2 x - 2log2 x )^2 + 36log2 x + 45<18log2^2 x
Ответ(ы) на вопрос:
Гость
[latex]\displaystyle (log_2^2x-2log_2x)^2+36log_2x+45\ \textless \ 18log_2^2x[/latex]
[latex]\displaystyle (log_2^2x-2log_2x)^2-18(log_2^2x-2log_2x)+45\ \textless \ 0[/latex]
[latex]\displaystyle Log_2^2x-2log_2x=t[/latex]
[latex]\displaystyle t^2-18t+45\ \textless \ 0[/latex]
[latex]\displaystyle D=324-180=144=12^2 t_P1=15; t_2=3[/latex]
__+_____-_____+____
3 15
[latex]\displaystyle \left \{ {{Log_2^2x-2log_2x\ \textless \ 15} \atop {log_2^2x-2log^2x\ \textgreater \ 3}} \right. [/latex]
1)
[latex]\displaystyle log_2^2x-2log_2x-15\ \textless \ 0[/latex]
[latex]\displaystyle D=4+64=64=8^2 [/latex]
_+____-_____+____
-3 5
[latex]\displaystyle -3\ \textless \ log_2x\ \textless \ 5[/latex]
[latex]\displaystyle \frac{1}{2^3}\ \textless \ x\ \textless \ 2^5 [/latex]
2)
[latex]\displaystyle log_2^2x-2log_2x-3\ \textgreater \ 0[/latex]
[latex]\displaystyle D=4^2[/latex]
__+___-____+___
-1 3
[latex]\displaystyle \left \{ {{log_2x\ \textgreater \ 3} \atop {log_2x\ \textless \ -1}} \right. [/latex]
[latex]\displaystyle \left \{ {{x\ \textless \ \frac{1}{2}} \atop {x\ \textgreater \ 2^5}} \right. [/latex]
Объединим все промежутки с учетом ОДЗ х>0
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0 1/8 1/2 8 32
ОТВЕТ: (1/8; 1/2) ∪(8;32)
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