Difference between revisions of "1956 AHSME Problems/Problem 23"

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The discriminant is equal to 0, so this simplifies to <math>x = \frac{2\sqrt{2}}{2a}=\frac{\sqrt{2}}{a}.</math> Because we are given that <math>a</math> is real, <math>x</math> is always real, and the answer is <math>\boxed{\textbf{(C)}}.</math>
 
The discriminant is equal to 0, so this simplifies to <math>x = \frac{2\sqrt{2}}{2a}=\frac{\sqrt{2}}{a}.</math> Because we are given that <math>a</math> is real, <math>x</math> is always real, and the answer is <math>\boxed{\textbf{(C)}}.</math>
  
~ cxsmi (significant edits)
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~ [https://artofproblemsolving.com/wiki/index.php/User:Cxsmi cxsmi] (significant edits)
  
 
==See Also==
 
==See Also==

Latest revision as of 13:47, 4 April 2024

Problem 23

About the equation $ax^2 - 2x\sqrt {2} + c = 0$, with $a$ and $c$ real constants, we are told that the discriminant is zero. The roots are necessarily:

$\textbf{(A)}\ \text{equal and integral}\qquad \textbf{(B)}\ \text{equal and rational}\qquad \textbf{(C)}\ \text{equal and real} \\ \textbf{(D)}\ \text{equal and irrational} \qquad \textbf{(E)}\ \text{equal and imaginary}$


Solution

Plugging into the quadratic formula, we get \[x = \frac{2\sqrt{2} \pm \sqrt{8-4ac}}{2a}.\] The discriminant is equal to 0, so this simplifies to $x = \frac{2\sqrt{2}}{2a}=\frac{\sqrt{2}}{a}.$ Because we are given that $a$ is real, $x$ is always real, and the answer is $\boxed{\textbf{(C)}}.$

~ cxsmi (significant edits)

See Also

1956 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 22
Followed by
Problem 24
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
All AHSME Problems and Solutions


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