If $x = {\log _b}a,\,\,y = {\log _c}b,\,\,\,z = {\log _a}c$, then $xyz$ is

Let $\quad \sum \limits_{n=0}^{\infty} \frac{n^3((2 n) !)+(2 n-1)(n !)}{(n !)((2 n) !)}=a e+\frac{b}{e}+c$, where $a, b, c \in Z$ and $e=\sum \limits_{n=0}^{\infty} \frac{1}{n!}$ Then $a^2-b+c$ is equal to $................$.

If ${\log _e}\left( {{{a + b} \over 2}} \right) = {1 \over 2}({\log _e}a + {\log _e}b)$, then relation between $a$ and $b$ will be

If ${\log _7}2 = m,$ then ${\log _{49}}28$ is equal to

Let $S$ be the sum of the digits of the number $15^2 \times 5^{18}$ in base $10$. Then,

The sum of all the natural numbers for which $log_{(4-x)}(x^2 -14x + 45)$ is defined is -