Difference between revisions of "2024 AIME I Problems/Problem 2"

Line 22: Line 22:
 
Convert the two equations into exponents.
 
Convert the two equations into exponents.
 
\begin{align*}
 
\begin{align*}
x^{10}=y^x \\
+
x^{10}=y^x\\
y^{10}=x^{4y} \\
+
y^{10}=x^{4y}\\
 
\end{align*}
 
\end{align*}
  

Revision as of 18:42, 2 February 2024

Problem

There exist real numbers $x$ and $y$, both greater than 1, such that $\log_x\left(y^x\right)=\log_y\left(x^{4y}\right)=10$. Find $xy$.

Solution 1

By properties of logarithms, we can simplify the given equation to $x\log_xy=4y\log_yx=10$. Let us break this into two separate equations: \begin{align*} x\log_xy&=10 \\ 4y\log_yx&=10. \\ \end{align*} We multiply the two equations to get: \[4xy\left(\log_xy\log_yx\right)=100.\]

Also by properties of logarithms, we know that $\log_ab\cdot\log_ba=1$; thus, $\log_xy\cdot\log_yx=1$. Therefore, our equation simplifies to:

\[4xy=100\implies xy=\boxed{025}.\]

~Technodoggo

==Solution 2== (if you're bad at logs)

Convert the two equations into exponents. \begin{align*} x^{10}=y^x\\ y^{10}=x^{4y}\\ \end{align*}


See also

2024 AIME I (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All AIME Problems and Solutions

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