{"id":4037,"date":"2021-08-15T10:41:51","date_gmt":"2021-08-15T10:41:51","guid":{"rendered":"https:\/\/mathemerize.com\/?p=4037"},"modified":"2021-11-26T16:46:11","modified_gmt":"2021-11-26T11:16:11","slug":"logs-change-of-base-formula","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/logs-change-of-base-formula\/","title":{"rendered":"Logs Change of Base Formula | Logarithm"},"content":{"rendered":"
Here you will learn logs change of base formula in logarithm and logarithmic inequalities with example.<\/p>\n
Let’s begin –<\/p>\n
It can be stated as “quotient of the algorithm of two numbers is independent of their common base.”<\/p>\n
\nSymbolically, \\(log_b m\\) = \\(log_a m \\over log_a b\\), where a > 0 , \\(a\\neq1\\), b > 0, \\(b\\neq1\\).<\/p>\n<\/blockquote>\n\n\n
NOTE : <\/b><\/p>\n\t\t
\n\t\t (i) \\(log_b a\\) . \\(log_a b\\) = \\(log a \\over log b\\) . \\(log b \\over log a\\) = 1 ; Hence \\(log_b a\\)=\\(1 \\over log_a b\\)<\/span>
\n\t\t (ii) \\(a^{log_b c} \\) = \\(c^{log_b a} \\)
\n\t\t (iii) \\(log_{a^k} m\\) = \\(1\\over k\\)\\(log_a m\\) It is known as Base Power Formula.<\/b>
\n\t\t (iv) The base of the logarithm can be any positive number other than 1, but in normal practice, only two bases are popular, these are 10 and e(=2.718 approx.). Logarithms of numbers to the base 10 are named as ‘common logarithm’ and the logarithms of numbers to the base e are called Natural or Napierian logarithm. We will consider logx as \\(log_e x\\) or lnx.<\/b>
<\/p>\n\n\n\nExample : <\/span> Evaluate the given log : \\(81^{l\\over {log_5 3}}\\) + \\(27^{log_9 36}\\) + \\(3^{4\\over {log_7 9}}\\).<\/p>\n
Solution : <\/span>\\(81^{log_3 5}\\) + \\(3^{3log_9 36}\\) + \\(3^{4log_9 7}\\)
\n\\(\\implies\\) \\(3^{4log_3 5}\\) + \\(3^{log_3 {(36)}^{3\/2}}\\) + \\(3^{log_3 {7}^2}\\)
\n= 625 + 216 + 49
= 890.
<\/p>\n\n\nNote :<\/strong><\/p>\n
\n(i) for a given value of N,\\(log_aN\\) will give us a unique value.<\/p>\n
(ii) Logarithm of zero does not exist.<\/p>\n
(iii) Logarithm of negative reals are not defined in the system of real numbers.<\/p>\n<\/blockquote>\n
Logarithmic Inequalities<\/h2>\n\n\n
(i) \\(log_a x\\) < \\(log_a y\\) <=> [ x < y if a > 1 && x > y if 0 < a < 1 ]
\n (ii) If a > 1, then (a) \\(log_a x\\) < p => 0 < x < \\(a^p\\) (b) \\(log_a x\\) > p => x > \\(a^p\\)
\n (iii) If 0 < a < 1, then (a) \\(log_a x\\) < p => x > \\(a^p\\) (b) \\(log_a x\\) > p => 0 < x < \\(a^p\\)\n
<\/p>\n\n\nHope you learnt logs change of base formula in logarithm. To learn more practice more questions and get ahead in competition. Good Luck!<\/p>\n\n\n