Difference between revisions of "1966 AHSME Problems/Problem 12"

(Solution)
(Solution)
Line 5: Line 5:
  
 
== Solution ==
 
== Solution ==
<math>\fbox{E}</math>
+
We know that
 +
<math>2^{6x+3}*4^{3x+6}=2^{6x+3}*(2^2)^{3x+6}=2^{6x+3}*2^{6x+12}=2^{12x+15}</math>.
 +
We also know that
 +
<math>8^{4x+5}=(2^3)^{4x+5}=2^{12x+15}</math>.
 +
Thus there are infinite solutions to this equation since <math>2^{12x+15}</math> is always equal to <math>2^{12x+15}</math>.
  
 
== See also ==
 
== See also ==

Revision as of 22:17, 12 September 2015

Problem

The number of real values of $x$ that satisfy the equation \[(2^{6x+3})(4^{3x+6})=8^{4x+5}\] is:

$\text{(A)  zero} \qquad \text{(B)  one} \qquad \text{(C)  two} \qquad \text{(D)  three} \qquad \text{(E)  greater than 3}$

Solution

We know that $2^{6x+3}*4^{3x+6}=2^{6x+3}*(2^2)^{3x+6}=2^{6x+3}*2^{6x+12}=2^{12x+15}$. We also know that $8^{4x+5}=(2^3)^{4x+5}=2^{12x+15}$. Thus there are infinite solutions to this equation since $2^{12x+15}$ is always equal to $2^{12x+15}$.

See also

1966 AHSME (ProblemsAnswer KeyResources)
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
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