Difference between revisions of "1977 AHSME Problems/Problem 21"

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For how many values of the coefficient a do the equations <cmath>\begin{align*}x^2+ax+1=0 \\ x^2-x-a=0\end{align*}</cmath> have a common real solution?
 
For how many values of the coefficient a do the equations <cmath>\begin{align*}x^2+ax+1=0 \\ x^2-x-a=0\end{align*}</cmath> have a common real solution?
  
<math>\textbf{(A)}\ 0 \qquad
+
$\textbf{(A)}\ 0 \qquad
 
\textbf{(B)}\ 1 \qquad
 
\textbf{(B)}\ 1 \qquad
 
\textbf{(C)}\ 2 \qquad
 
\textbf{(C)}\ 2 \qquad
 
\textbf{(D)}\ 3 \qquad
 
\textbf{(D)}\ 3 \qquad
\textbf{(E)}\ \infty</math>
+
\textbf{(E)}\ \infty

Revision as of 05:07, 23 February 2023

Problem 21

For how many values of the coefficient a do the equations \begin{align*}x^2+ax+1=0 \\ x^2-x-a=0\end{align*} have a common real solution?

$\textbf{(A)}\ 0 \qquad \textbf{(B)}\ 1 \qquad \textbf{(C)}\ 2 \qquad \textbf{(D)}\ 3 \qquad \textbf{(E)}\ \infty