Difference between revisions of "2021 Fall AMC 10A Problems/Problem 14"

(Solution (Graphing))
(Solution (Graphing))
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<asy>
 
<asy>
import graph;
+
 
 
Label f;  
 
Label f;  
 
f.p=fontsize(6);  
 
f.p=fontsize(6);  
 
xaxis(-8,8,Ticks(f, 2.0,0.5));  
 
xaxis(-8,8,Ticks(f, 2.0,0.5));  
yaxis(-8,8,Ticks(f, 2.0,0.5))
+
yaxis(-8,8,Ticks(f, 2.0,0.5));
 
 
 
 
  
 
</asy>
 
</asy>

Revision as of 20:04, 23 November 2021

Problem

How many ordered pairs $(x,y)$ of real numbers satisfy the following system of equations? \[x^2+3y=9\] \[(|x|+|y|-4)^2 = 1\]

$\textbf{(A )} 1 \qquad\textbf{(B) } 2 \qquad\textbf{(C) } 3 \qquad\textbf{(D) } 5 \qquad\textbf{(E) } 7$


Solution (Graphing)

The second equation is $(|x|+|y| - 4)^2 = 1$. We know that the graph of $|x| + |y|$ is a very simple diamond shape, so let's see if we can reduce this equation to that form.

$(|x|+|y| - 4)^2 = 1 \implies |x|+|y| - 4 = \pm 1 \implies |x|+|y| = \{3,5$}.

We now have two separate graphs for this equation and one graph for the first equation, so let's put it on the coordinate plane:


[asy]  Label f;  f.p=fontsize(6);  xaxis(-8,8,Ticks(f, 2.0,0.5));  yaxis(-8,8,Ticks(f, 2.0,0.5));  [/asy]

See Also

2021 Fall AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 13
Followed by
Problem 15
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
All AMC 10 Problems and Solutions

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