Difference between revisions of "1960 AHSME Problems/Problem 11"
Rockmanex3 (talk | contribs) (Created page with "==Problem== For a given value of <math>k</math> the product of the roots of <math>x^2-3kx+2k^2-1=0</math> is <math>7</math>. The roots may be characterized as: <math>\textbf...") |
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==See Also== | ==See Also== | ||
| − | {{AHSME box|year=1960|num-b=10|num-a=12}} | + | {{AHSME 40p box|year=1960|num-b=10|num-a=12}} |
Revision as of 19:13, 10 May 2018
Problem
For a given value of 
the product of the roots of 
is 
. The roots may be characterized as:
Solution
If the product of the roots are , then by Vieta's formulas,
![\[2k^2-1=7\]](http://latex.artofproblemsolving.com/c/0/c/c0c3333c39193ed9c82a2c1d8614462df0f82b19.png)
Solve for in the resulting equation to get
![\[2k^2=8\]](http://latex.artofproblemsolving.com/1/c/d/1cd6df4d9d808a623f22dc841ef903a6b01cd1c1.png)
![\[k^2=4\]](http://latex.artofproblemsolving.com/4/6/4/4646a39d57b77763bb40188214fa33f2f3452f30.png)
![\[k=\pm 2\]](http://latex.artofproblemsolving.com/4/6/e/46e1269909a413132acf81c55772bd4ac7296bbd.png)
That means the two quadratics are 
and 
. Since 
, 
, and 
are the same, the discriminant of both is
. Because 
is not a perfect square, the roots for both are irrational, so the answer is 
.
See Also
| 1960 AHSC (Problems • Answer Key • Resources) | ||
| Preceded by Problem 10 |
Followed by Problem 12 | |
| 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 | ||
| All AHSME Problems and Solutions | ||
