2023 IOQM/Problem 2

Revision as of 20:36, 2 October 2023 by Sansgankrsngupta (talk | contribs) (Solution quick)

Problem

Find the number of elements in the set

\[\lbrace(a.b)\in N: 2 \leq a,b \leq2023,\:\: \log_{a}{b}+6\log_{b}{a}=5\rbrace\]

Solution quick

$\log_{a}{b}=x$ Then, $x$+$\frac{5}{x}$ =6. Upon solving the equation


So, x equals to 2 or 3

For 2, it's obvious that there are {2,4}...{44,1936}

For 3, it's obvious that there are {2,8}...{12,1728}

Thus, there are 43+11=54 pairs