1.8-bo'lim : Logarifm funktsiyalari
12. \(\displaystyle \frac{1}{3}\log a - 6\log b + 2\) ni bitta koeffitsientli bitta logarifmaga birlashtiring.
Yechim
Buni bitta logarifmaga aylantirish uchun biz logarifmlarni teskari yo'nalishda ajratish uchun ishlatgan xususiyatlardan foydalanamiz. Ushbu jarayondagi birinchi qadam mulkdan foydalanish,
\[{\log _b}\left( {{x^r}} \right) = r{\log _b}x\]barcha logarifmlar bitta koeffitsientga ega ekanligiga ishonch hosil qilish. Buni birinchi navbatda qilish kerak, chunki logarifmlarning yig'indisini/farqlarini birlashtirishga imkon beradigan barcha xususiyatlar alohida logarifmlarda bitta koeffitsientni talab qiladi. Shunday qilib, ushbu xususiyatdan foydalanish,
\[\log \left( {{a^{\frac{1}{3}}}} \right) - \log \left( {{b^6}} \right) + 2\]Endi, 2-ga e'tibor bering, buni logarifm shaklida quyidagicha yozishimiz mumkin:
\[2 = \log {10^2} = \log 100\]E'tibor bering, bu haqiqatan ham mulkdan foydalanmoqda,
\[{\log _b}{b^x} = x\]Demak, endi bizda,
\[\log \left( {{a^{\frac{1}{3}}}} \right) - \log \left( {{b^6}} \right) + \log 100\]Endi bu nuqtadan chiqishning bir necha yo'li mavjud. Biz ikkita xususiyatdan birini ishlatishimiz mumkin.
\[{\log _b}\left( {xy} \right) = {\log _b}x + {\log _b}y\hspace{0.75in}{\log _b}\left( {\frac{x}{y}} \right) = {\log _b}x - {\log _b}y\]va aslida biz oxirida ikkalasini ham ishlatishimiz kerak bo'ladi. Qaysi biri birinchi bo'lib qo'llanilishi muhim emas, chunki oxirida biz bir xil natijaga erishamiz. Mana, bu muammo uchun ishning qolgan qismi.
\[\begin{align*}\log \left( {{a^{\frac{1}{3}}}} \right) - \log \left( {{b^6}} \right) + \log {10^2} & = \log \left( {100\,\sqrt[3]{a}} \right) - \log \left( {{b^6}} \right)\\ & = \require{bbox} \bbox[2pt,border:1px solid black]{{\log \left( {\frac{{100\,\sqrt[3]{a}}}{{{b^6}}}} \right)}}\end{align*}\]E'tibor bering, kasr ko'rsatkichini ildizga o'tkazishimizning yagona sababi yakuniy javobni biroz chiroyli qilish edi.