Difference between revisions of "2021 AIME II Problems/Problem 4"

(Solution 3)
(Solution 3 (Somewhat Bashy))
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==Solution 2==
 
==Solution 2==
 
==Solution 3 (Somewhat Bashy)==
 
==Solution 3 (Somewhat Bashy)==
 +
<math>(-20)^{3} + (-20)a + b = 0</math>, hence <math>-20a + b = 8000</math>
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 +
Also, <math>(-21)^{3} + c(-21)^{2} + d = 0</math>, hence <math>441c + d = 9261</math>
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<math>m + i \sqrt{n}</math>
  
 
==See also==
 
==See also==
 
{{AIME box|year=2021|n=II|num-b=3|num-a=5}}
 
{{AIME box|year=2021|n=II|num-b=3|num-a=5}}
 
{{MAA Notice}}
 
{{MAA Notice}}

Revision as of 01:25, 23 March 2021

Problem

There are real numbers $a, b, c,$ and $d$ such that $-20$ is a root of $x^3 + ax + b$ and $-21$ is a root of $x^3 + cx^2 + d.$ These two polynomials share a complex root $m + \sqrt{n} \cdot i,$ where $m$ and $n$ are positive integers and $i = \sqrt{-1}.$ Find $m+n.$

Solution 1

Conjugate root theorem

Solution in progress

~JimY

Solution 2

Solution 3 (Somewhat Bashy)

$(-20)^{3} + (-20)a + b = 0$, hence $-20a + b = 8000$

Also, $(-21)^{3} + c(-21)^{2} + d = 0$, hence $441c + d = 9261$

$m + i \sqrt{n}$

See also

2021 AIME II (ProblemsAnswer KeyResources)
Preceded by
Problem 3
Followed by
Problem 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All AIME Problems and Solutions

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