Difference between revisions of "2021 AMC 12B Problems/Problem 18"
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==Problem 18== | ==Problem 18== | ||
| − | Let <math>z</math> be a complex number satisfying <math>12|z|^2=2|z+2|^2+|z^2+1|^2+31.</math> What is the value | + | Let <math>z</math> be a complex number satisfying <math>12|z|^2=2|z+2|^2+|z^2+1|^2+31.</math> What is the value of <math>z+\frac 6z?</math> |
<math>\textbf{(A) }-2 \qquad \textbf{(B) }-1 \qquad \textbf{(C) }\frac12\qquad \textbf{(D) }1 \qquad \textbf{(E) }4</math> | <math>\textbf{(A) }-2 \qquad \textbf{(B) }-1 \qquad \textbf{(C) }\frac12\qquad \textbf{(D) }1 \qquad \textbf{(E) }4</math> | ||
Revision as of 18:56, 11 February 2021
Problem 18
Let 
be a complex number satisfying 
What is the value of 
Solution
Solution 1
The answer being in the form 
means that there are two solutions, some complex number and its complex conjugate. ![\[a+bi = \frac{6}{a-bi}\]](http://latex.artofproblemsolving.com/5/f/3/5f333ff36bfce8cc1cbef23b56cdc66c678671eb.png)
![\[a^2+b^2=6\]](http://latex.artofproblemsolving.com/a/0/0/a006fc3bc9d7d0863ef53f8dd41755cca1848ac8.png)
We should then be able to test out some ordered pairs of (a, b). After testing it out, we get the ordered pairs of 
and its conjugate 
. Plugging this into answer format gives us 
~Lopkiloinm
