Difference between revisions of "2000 SMT/Algebra Problems/Problem 2"

(Solution 1 - SUBMITTED BY HOWDOI_YT)
 
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Problem 2
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==Problem 2==
  
Evaluate 2000^3 - 1999(2000^2) - 1999^2(2000) + 1999^3
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Evaluate <math>2000^3 - 1999(2000^2) - 1999^2(2000) + 1999^3</math>
  
Solution 1 - SUBMITTED BY HOWDOI_YT
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==Solution 1 - Submitted by howdoi_yt==
  
I can write the first 1999 as 2000-1, and the 3rd 2000 as 1999+1;
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I can rewrite the first <math>1999</math> as <math>(2000-1)</math>, and the third <math>2000</math> as <math>(1999+1)</math>;
2000^3 - 2000^2(2000-1) - 1999^2(1999+1) + 1999^3 = 2000^3 - 2000^3 + 2000^2 - 1999^3 - 1999^2 + 1999^3 = 2000^2 - 1999^2 = (2000 - 1999)(2000 + 1999) = **3999** \qed
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(oml i just realized how bad this looks someone help me edit it lmao)
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<math>2000^3 - 2000^2(2000-1) - 1999^2(1999+1) + 1999^3</math>
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<math>= 2000^3 - 2000^3 + 2000^2 - 1999^3 - 1999^2 + 1999^3</math>
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<math>= 2000^2 - 1999^2</math>
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<math>= (2000 - 1999)(2000 + 1999)</math>
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<math>= 3999 \qquad \blacksquare</math>

Latest revision as of 15:14, 18 April 2023

Problem 2

Evaluate $2000^3 - 1999(2000^2) - 1999^2(2000) + 1999^3$

Solution 1 - Submitted by howdoi_yt

I can rewrite the first $1999$ as $(2000-1)$, and the third $2000$ as $(1999+1)$;

$2000^3 - 2000^2(2000-1) - 1999^2(1999+1) + 1999^3$

$= 2000^3 - 2000^3 + 2000^2 - 1999^3 - 1999^2 + 1999^3$

$= 2000^2 - 1999^2$

$= (2000 - 1999)(2000 + 1999)$

$= 3999 \qquad \blacksquare$