14310: Difference between revisions
Benzar Ioan (talk | contribs) Created page with "'''14310 (Traian Covaciu)''' ''Fie <math>n, n + 2, n + 6 </math> trei numere naturale și <math> S </math> suma lor.'' a) ''Dați exemplu de cel puțin trei valori pentru <math> n \in \mathbb{N}</math> astfel incat numerele <math> n, n + 2, n + 6 </math> sa fie simultan numere prime.'' <p> b) ''Daca <math> n, n + 2, n + 6 </math> sunt simultan numere prime, aratati ca exista <math> k \in \mathbb{N} </math> astfel incat <math> S = 9k + 5</math>. '' <p> c) ''Daca <math..." |
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''Fie <math>n, n + 2, n + 6 </math> trei numere naturale și <math> S </math> suma lor.'' | ''Fie <math>n, n + 2, n + 6 </math> trei numere naturale și <math> S </math> suma lor.'' | ||
a) ''Dați exemplu de cel puțin trei valori pentru <math> n \in \mathbb{N}</math> astfel | a) ''Dați exemplu de cel puțin trei valori pentru <math> n \in \mathbb{N}</math> astfel încât numerele <math> n, n + 2, n + 6 </math> să fie simultan numere prime.'' <p> | ||
b) '' | b) ''Dacă <math> n, n + 2, n + 6 </math> sunt simultan numere prime, arătați că există <math> k \in \mathbb{N} </math> astfel încât <math> S = 9k + 5</math>. '' <p> | ||
c) '' | c) ''Dacă <math> n, n + 2, n + 6 </math> sunt numere prime, determinați restul împărțirii numărului <math> S</math> la <math> 18 </math>.'' | ||
<p> | <p> | ||
''' | '''Soluție:''' <p> | ||
a) Pentru <math> n = 5 </math> numerele sunt <math> 5, 7, 11 </math>. Pentru <math> n = 11 </math> avem <math> 11, 13, 17 </math>, iar pentru <math> n = 17 </math> | a) Pentru <math> n = 5 </math> numerele sunt <math> 5, 7, 11 </math>. Pentru <math> n = 11 </math> avem <math> 11, 13, 17 </math>, iar pentru <math> n = 17 </math> obținem <math> 17, 19, 23 </math>. <p> | ||
b) Se | b) Se știe că numerele prime au forma <math> 6p + 1 </math> sau <math> 6p + 5 </math>. Dacă <math> n = 6p + 1</math>, atunci <math> n + 2 = 6p + 3 </math> care nu este numar prim. Așadar, <math> n = 6p + 5 </math>. În această situație avem <math> S = 6p + 5 + 6p + 7 + 6p + 11 = 18p + 23 = 9(2p + 2) + 5 </math>. În concluzie, există <math> k = 2p + 2 </math> astfel încât <math> S = 9k + 5 </math>. <p> | ||
c) Din punctul b) avem <math> S = 18(p + 1) + 5 </math>, deci restul | c) Din punctul b) avem <math> S = 18(p + 1) + 5 </math>, deci restul împărțirii lui <math> S </math> la <math> 18 </math> este <math> 5 </math>. | ||
Revision as of 17:58, 12 January 2025
14310 (Traian Covaciu)
Fie Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n, n + 2, n + 6 } trei numere naturale și Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S } suma lor.
a) Dați exemplu de cel puțin trei valori pentru Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n \in \mathbb{N}} astfel încât numerele Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n, n + 2, n + 6 } să fie simultan numere prime.
b) Dacă Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n, n + 2, n + 6 } sunt simultan numere prime, arătați că există Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle k \in \mathbb{N} } astfel încât Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S = 9k + 5} .
c) Dacă Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n, n + 2, n + 6 } sunt numere prime, determinați restul împărțirii numărului Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S} la Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 18 } .
Soluție:
a) Pentru Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n = 5 } numerele sunt Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 5, 7, 11 } . Pentru Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n = 11 } avem Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 11, 13, 17 } , iar pentru Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n = 17 } obținem Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 17, 19, 23 } .
b) Se știe că numerele prime au forma Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 6p + 1 } sau Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 6p + 5 } . Dacă Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n = 6p + 1} , atunci Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n + 2 = 6p + 3 } care nu este numar prim. Așadar, Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle n = 6p + 5 } . În această situație avem Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S = 6p + 5 + 6p + 7 + 6p + 11 = 18p + 23 = 9(2p + 2) + 5 } . În concluzie, există Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle k = 2p + 2 } astfel încât Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S = 9k + 5 } .
c) Din punctul b) avem Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S = 18(p + 1) + 5 } , deci restul împărțirii lui Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle S } la Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 18 } este Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 5 } .