Difference between revisions of "Euclid 2019/Problem 5"

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==Problem==
 
==Problem==
  
(a) Determine the two pairs of positive integers <math>(a,b)</math> with <math>a<b</math> that satisfy the equation <math>\sqrt a+\sqrt b=\sqrt 50</math>.
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(a) Determine the two pairs of positive integers <math>(a,b)</math> with <math>a<b</math> that satisfy the equation <math>\sqrt a+\sqrt b=\sqrt (50)</math>.
  
 
(b) Consider the system of equations: <math>c+d=2000</math> and <math>\frac{c}{d}=k</math>. Determine the number of integers <math>k</math> with <math>k\leq0</math> for which there is at least one pair of integers <math>(c,d)</math> that is a solution to the system.
 
(b) Consider the system of equations: <math>c+d=2000</math> and <math>\frac{c}{d}=k</math>. Determine the number of integers <math>k</math> with <math>k\leq0</math> for which there is at least one pair of integers <math>(c,d)</math> that is a solution to the system.
  
 
==Solution==
 
==Solution==
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(a) <math>\sqrt(50)=5\sqrt(2)</math>, and <math>5\sqrt(2)</math> can be expressed as <math>\sqrt(2)+4\sqrt(2)</math>, or <math>2\sqrt(2)+3\sqrt(2)</math>.
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From the first equation, we get that <math>\sqrt(2)+\sqrt(32)</math>, and from the second of these equations, we have <math>\sqrt(8)+\sqrt(18)</math>. So our solutions for <math>(a,b)</math> are <math>\boxed{(2,32), (8,18)}</math>.

Latest revision as of 14:25, 13 October 2025

Problem

(a) Determine the two pairs of positive integers $(a,b)$ with $a<b$ that satisfy the equation $\sqrt a+\sqrt b=\sqrt (50)$.

(b) Consider the system of equations: $c+d=2000$ and $\frac{c}{d}=k$. Determine the number of integers $k$ with $k\leq0$ for which there is at least one pair of integers $(c,d)$ that is a solution to the system.

Solution

(a) $\sqrt(50)=5\sqrt(2)$, and $5\sqrt(2)$ can be expressed as $\sqrt(2)+4\sqrt(2)$, or $2\sqrt(2)+3\sqrt(2)$. From the first equation, we get that $\sqrt(2)+\sqrt(32)$, and from the second of these equations, we have $\sqrt(8)+\sqrt(18)$. So our solutions for $(a,b)$ are $\boxed{(2,32), (8,18)}$.