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Basic of Logarithms
medium
यदि ${\log _7}2 = m,$ हो, तब ${\log _{49}}28$ बराबर होगा
A
$2\,(1 + 2m)$
B
$\frac{{1 + 2m}}{2}$
C
$\frac{2}{{1 + 2m}}$
D
$1 + m$
Solution
${\log _{49}}28 = \frac{{\log 28}}{{\log 49}} = \frac{{\log 7 + \log 4}}{{2\log 7}}$=$\frac{{\log 7}}{{2\log 7}} + \frac{{\log 4}}{{2\log 7}} = \frac{1}{2} + \frac{1}{2}{\log _7}4$ = $\frac{1}{2} + \frac{1}{2}.2{\log _7}2$=$\frac{1}{2} + {\log _7}2 = \frac{1}{2} + m$$ = \frac{{1 + 2m}}{2}$
Standard 11
Mathematics