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Basic of Logarithms
medium
સમીકરણ ${\log _7}{\log _5}$ $(\sqrt {{x^2} + 5 + x} ) = 0$ નો ઉકેલ મેળવો.
A
$x = 2$
B
$x = 3$
C
$x = 4$
D
$x = - 2$
Solution
(c) ${\log _7}{\log _5}(\sqrt {{x^2} + 5 + x} ) = 0 = {\log _7}1$
$ \Rightarrow $ ${({x^2} + 5 + x)^{1/2}} = 5$
$ \Rightarrow $ $({x^2} + x + 5) = 25$ $ \Rightarrow $ ${x^2} + x – 20 = 0$
$ \Rightarrow $ $(x – 4)\,(x + 5) = 0$ $ \Rightarrow $$x = \,4,\, – 5$ ==> $x = 4$.
Standard 11
Mathematics
