Difference between revisions of "2022 AMC 10A Problems/Problem 6"

(Solution 3: Sorry to delete this solution, but this solution has the exact same idea as Sol 1...)
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-MathWizard09
 
-MathWizard09
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== Solution 3 ==
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Given function is continuous, so assume that <math>a=0.</math> Then, the given expression simplifies to <math>3.</math>
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We test each of the answer choices and get <math>\textbf{(A) } 3-2a</math> or <math>\textbf{(E) } 3.</math>
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We test <math>x = - 1000</math> and get  <math>\left|-1000-2- positive \right| \ne 3 \implies \boxed{\textbf{(A) } 3-2a}.</math>
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'''vladimir.shelomovskii@gmail.com, vvsss'''
  
 
==Video Solution 1 (Quick and Easy)==
 
==Video Solution 1 (Quick and Easy)==

Revision as of 12:41, 8 October 2023

Problem

Which expression is equal to \[\left|a-2-\sqrt{(a-1)^2}\right|\] for $a<0?$

$\textbf{(A) } 3-2a \qquad \textbf{(B) } 1-a \qquad \textbf{(C) } 1 \qquad \textbf{(D) } a+1 \qquad \textbf{(E) } 3$

Solution 1

We have \begin{align*} \left|a-2-\sqrt{(a-1)^2}\right| &= \left|a-2-|a-1|\right| \\ &=\left|a-2-(1-a)\right| \\ &=\left|2a-3\right| \\ &=\boxed{\textbf{(A) } 3-2a}. \end{align*} ~MRENTHUSIASM

Solution 2

Assume that $a=-1.$ Then, the given expression simplifies to $5$: \begin{align*} \left|a-2-\sqrt{(a-1)^2}\right| &= \left|-1-2-\sqrt{(-1-1)^2}\right| \\ &= \left|-1-2-\sqrt{4}\right| \\ &= \left|-1-2-2\right| \\ &= 5. \end{align*} Then, we test each of the answer choices to see which one is equal to $5$:

$\textbf{(A) } 3-2a = 3-2\cdot(-1) = 3+2 = 5.$

$\textbf{(B) } 1-a = 1-(-1) = 2 \neq 5.$

$\textbf{(C) } 1 \neq 5.$

$\textbf{(D) } a+1 = -1+1 = 0 \neq 5.$

$\textbf{(E) } 3 \neq 5.$

The only answer choice equal to $5$ for $a=-1$ is $\boxed{\textbf{(A) } 3-2a}.$

-MathWizard09

Solution 3

Given function is continuous, so assume that $a=0.$ Then, the given expression simplifies to $3.$

We test each of the answer choices and get $\textbf{(A) } 3-2a$ or $\textbf{(E) } 3.$

We test $x = - 1000$ and get $\left|-1000-2- positive \right| \ne 3 \implies \boxed{\textbf{(A) } 3-2a}.$

vladimir.shelomovskii@gmail.com, vvsss

Video Solution 1 (Quick and Easy)

https://youtu.be/ZWHzdrW4rvw

~Education, the Study of Everything

See Also

2022 AMC 10A (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
All AMC 10 Problems and Solutions

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