Difference between revisions of "1959 AHSME Problems/Problem 8"

m (see also box)
m (improved clarity)
 
Line 11: Line 11:
 
== Solution ==  
 
== Solution ==  
  
The <math>x</math> value at which the minimum value of this quadratic occurs is <math>-\frac{-6}{2\cdot1}=3</math>. The minimum value of the quadratic is therefore at
+
The <math>x</math> value at which the minimum value of this [[quadratic]] (of the form <math>ax^2+bx+c</math>) occurs is <math>\frac{-b}{2a}=-\frac{-6}{2\cdot1}=3</math>. The minimum value of the quadratic is therefore at
 
<cmath>3^2-6\cdot3+13</cmath>
 
<cmath>3^2-6\cdot3+13</cmath>
 
<cmath>=9-18+13</cmath>
 
<cmath>=9-18+13</cmath>

Latest revision as of 12:06, 21 July 2024

Problem

The value of $x^2-6x+13$ can never be less than:

$\textbf{(A)}\ 4 \qquad \textbf{(B)}\ 4.5 \qquad \textbf{(C)}\ 5\qquad \textbf{(D)}\ 7\qquad \textbf{(E)}\ 13$

Solution

The $x$ value at which the minimum value of this quadratic (of the form $ax^2+bx+c$) occurs is $\frac{-b}{2a}=-\frac{-6}{2\cdot1}=3$. The minimum value of the quadratic is therefore at \[3^2-6\cdot3+13\] \[=9-18+13\] \[=4.\] So, the answer is $\boxed{\textbf{(A)} \ 4}$.

See also

1959 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 7
Followed by
Problem 9
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 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
All AHSME Problems and Solutions

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png