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

Line 21: Line 21:
  
 
Convert the two equations into exponents:
 
Convert the two equations into exponents:
 
 
<cmath>x^{10}=y^x~(1)</cmath>
 
<cmath>x^{10}=y^x~(1)</cmath>
 
<cmath>y^{10}=x^{4y}~(2).</cmath>
 
<cmath>y^{10}=x^{4y}~(2).</cmath>
  
Take the top equation to the power of <math>\frac{1}{x}</math>.
+
Take <math>(1)</math> to the power of <math>\frac{1}{x}</math>:
  
 
<cmath>x^{\frac{10}{y}}=y.</cmath>
 
<cmath>x^{\frac{10}{y}}=y.</cmath>
 
Plug this into
 
Plug this into
 +
  
 
==See also==
 
==See also==

Revision as of 18:51, 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: xlogxy=104ylogyx=10. 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: \[x^{10}=y^x~(1)\] \[y^{10}=x^{4y}~(2).\]

Take $(1)$ to the power of $\frac{1}{x}$:

\[x^{\frac{10}{y}}=y.\] Plug this into


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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