81^(x-4)=1/3 (уравнение) Учитель очень удивится увидев твоё верное решение 😼
Найду корень уравнения: 81^(x-4)=1/3
Решение
Подробное решение
Дано уравнение:8 1 x − 4 = 1 3 81^{x - 4} = \frac{1}{3} 8 1 x − 4 = 3 1 или8 1 x − 4 − 1 3 = 0 81^{x - 4} - \frac{1}{3} = 0 8 1 x − 4 − 3 1 = 0 или8 1 x 43046721 = 1 3 \frac{81^{x}}{43046721} = \frac{1}{3} 43046721 8 1 x = 3 1 или8 1 x = 14348907 81^{x} = 14348907 8 1 x = 14348907 - это простейшее показательное ур-ние Сделаем заменуv = 8 1 x v = 81^{x} v = 8 1 x получимv − 14348907 = 0 v - 14348907 = 0 v − 14348907 = 0 илиv − 14348907 = 0 v - 14348907 = 0 v − 14348907 = 0 Переносим свободные слагаемые (без v) из левой части в правую, получим:v = 14348907 v = 14348907 v = 14348907 Получим ответ: v = 14348907 делаем обратную замену8 1 x = v 81^{x} = v 8 1 x = v илиx = log ( v ) log ( 81 ) x = \frac{\log{\left(v \right)}}{\log{\left(81 \right)}} x = log ( 81 ) log ( v ) Тогда, окончательный ответx 1 = log ( 14348907 ) log ( 81 ) = 15 4 x_{1} = \frac{\log{\left(14348907 \right)}}{\log{\left(81 \right)}} = \frac{15}{4} x 1 = log ( 81 ) log ( 14348907 ) = 4 15
График
-7.5 -5.0 -2.5 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 0 5000000000000000000
x 1 = 15 4 x_{1} = \frac{15}{4} x 1 = 4 15 log(14348907) pi*I
x2 = ------------- - --------
4*log(3) 2*log(3) x 2 = log ( 14348907 ) 4 log ( 3 ) − i π 2 log ( 3 ) x_{2} = \frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} - \frac{i \pi}{2 \log{\left(3 \right)}} x 2 = 4 log ( 3 ) log ( 14348907 ) − 2 log ( 3 ) iπ log(14348907) pi*I
x3 = ------------- + --------
4*log(3) 2*log(3) x 3 = log ( 14348907 ) 4 log ( 3 ) + i π 2 log ( 3 ) x_{3} = \frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} + \frac{i \pi}{2 \log{\left(3 \right)}} x 3 = 4 log ( 3 ) log ( 14348907 ) + 2 log ( 3 ) iπ 15 pi*I
x4 = -- + ------
4 log(3) x 4 = 15 4 + i π log ( 3 ) x_{4} = \frac{15}{4} + \frac{i \pi}{\log{\left(3 \right)}} x 4 = 4 15 + log ( 3 ) iπ
Сумма и произведение корней
[src] log(14348907) pi*I log(14348907) pi*I 15 pi*I
0 + 15/4 + ------------- - -------- + ------------- + -------- + -- + ------
4*log(3) 2*log(3) 4*log(3) 2*log(3) 4 log(3) ( ( ( 0 + 15 4 ) + ( log ( 14348907 ) 4 log ( 3 ) − i π 2 log ( 3 ) ) ) + ( log ( 14348907 ) 4 log ( 3 ) + i π 2 log ( 3 ) ) ) + ( 15 4 + i π log ( 3 ) ) \left(\left(\left(0 + \frac{15}{4}\right) + \left(\frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} - \frac{i \pi}{2 \log{\left(3 \right)}}\right)\right) + \left(\frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} + \frac{i \pi}{2 \log{\left(3 \right)}}\right)\right) + \left(\frac{15}{4} + \frac{i \pi}{\log{\left(3 \right)}}\right) ( ( ( 0 + 4 15 ) + ( 4 log ( 3 ) log ( 14348907 ) − 2 log ( 3 ) iπ ) ) + ( 4 log ( 3 ) log ( 14348907 ) + 2 log ( 3 ) iπ ) ) + ( 4 15 + log ( 3 ) iπ ) 15 log(14348907) pi*I
-- + ------------- + ------
2 2*log(3) log(3) 15 2 + log ( 14348907 ) 2 log ( 3 ) + i π log ( 3 ) \frac{15}{2} + \frac{\log{\left(14348907 \right)}}{2 \log{\left(3 \right)}} + \frac{i \pi}{\log{\left(3 \right)}} 2 15 + 2 log ( 3 ) log ( 14348907 ) + log ( 3 ) iπ /log(14348907) pi*I \ /log(14348907) pi*I \ /15 pi*I \
1*15/4*|------------- - --------|*|------------- + --------|*|-- + ------|
\ 4*log(3) 2*log(3)/ \ 4*log(3) 2*log(3)/ \4 log(3)/ 1 ⋅ 15 4 ( log ( 14348907 ) 4 log ( 3 ) − i π 2 log ( 3 ) ) ( log ( 14348907 ) 4 log ( 3 ) + i π 2 log ( 3 ) ) ( 15 4 + i π log ( 3 ) ) 1 \cdot \frac{15}{4} \left(\frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} - \frac{i \pi}{2 \log{\left(3 \right)}}\right) \left(\frac{\log{\left(14348907 \right)}}{4 \log{\left(3 \right)}} + \frac{i \pi}{2 \log{\left(3 \right)}}\right) \left(\frac{15}{4} + \frac{i \pi}{\log{\left(3 \right)}}\right) 1 ⋅ 4 15 ( 4 log ( 3 ) log ( 14348907 ) − 2 log ( 3 ) iπ ) ( 4 log ( 3 ) log ( 14348907 ) + 2 log ( 3 ) iπ ) ( 4 15 + log ( 3 ) iπ ) 15*(-2*pi*I + log(14348907))*(2*pi*I + log(14348907))*(4*pi*I + log(14348907))
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3
256*log (3) 15 ( log ( 14348907 ) − 2 i π ) ( log ( 14348907 ) + 2 i π ) ( log ( 14348907 ) + 4 i π ) 256 log ( 3 ) 3 \frac{15 \left(\log{\left(14348907 \right)} - 2 i \pi\right) \left(\log{\left(14348907 \right)} + 2 i \pi\right) \left(\log{\left(14348907 \right)} + 4 i \pi\right)}{256 \log{\left(3 \right)}^{3}} 256 log ( 3 ) 3 15 ( log ( 14348907 ) − 2 iπ ) ( log ( 14348907 ) + 2 iπ ) ( log ( 14348907 ) + 4 iπ ) x2 = 3.75 - 1.42980043369006*i x3 = 3.75 + 1.42980043369006*i x4 = 3.75 + 2.85960086738013*i