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

(Solution 1 - SUBMITTED BY HOWDOI_YT)
 
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Evaluate <math>2000^3 - 1999(2000^2) - 1999^2(2000) + 1999^3</math>
 
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 rewrite the first <math>1999</math> as <math>(2000-1)</math>, and the third <math>2000</math> as <math>(1999+1)</math>;
  
I can write the first <math>1999</math> as <math>2000-1</math>, and the 3rd <math>2000</math> as <math>1999+1</math>;
 
 
<math>2000^3 - 2000^2(2000-1) - 1999^2(1999+1) + 1999^3</math>
 
<math>2000^3 - 2000^2(2000-1) - 1999^2(1999+1) + 1999^3</math>
 +
 
<math>= 2000^3 - 2000^3 + 2000^2 - 1999^3 - 1999^2 + 1999^3</math>
 
<math>= 2000^3 - 2000^3 + 2000^2 - 1999^3 - 1999^2 + 1999^3</math>
 +
 
<math>= 2000^2 - 1999^2</math>
 
<math>= 2000^2 - 1999^2</math>
 +
 
<math>= (2000 - 1999)(2000 + 1999)</math>
 
<math>= (2000 - 1999)(2000 + 1999)</math>
<math>= 3999 \blacksquare</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 $(1999+1)$;

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

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

$= 2000^2 - 1999^2$

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

$= 3999 \qquad \blacksquare$