Difference between revisions of "1980 AHSME Problems/Problem 6"

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<math> \sqrt{x}< 2x \\ x < 4x^2 \\ 0 < x(4x-1) \\ 0 < 4x-1 \\ 1 < 4x \\ x >\frac{1}{4} \\ \boxed{(A)}</math>
 
<math> \sqrt{x}< 2x \\ x < 4x^2 \\ 0 < x(4x-1) \\ 0 < 4x-1 \\ 1 < 4x \\ x >\frac{1}{4} \\ \boxed{(A)}</math>
  
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Note: You can also draw a rough sketch.
  
 
== See also ==
 
== See also ==
 
{{AHSME box|year=1980|num-b=5|num-a=7}}
 
{{AHSME box|year=1980|num-b=5|num-a=7}}
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{{MAA Notice}}

Latest revision as of 15:40, 20 March 2018

Problem

A positive number $x$ satisfies the inequality $\sqrt{x} < 2x$ if and only if

$\text{(A)} \ x > \frac{1}{4} \qquad \text{(B)} \ x > 2 \qquad \text{(C)} \ x > 4 \qquad \text{(D)} \ x < \frac{1}{4}\qquad \text{(E)} \ x < 4$

Solution

$\sqrt{x}< 2x \\ x < 4x^2 \\ 0 < x(4x-1) \\ 0 < 4x-1 \\ 1 < 4x \\ x >\frac{1}{4} \\ \boxed{(A)}$

Note: You can also draw a rough sketch.

See also

1980 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 5
Followed by
Problem 7
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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