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| Calculer Uo et la raison r? http://xn--forum-franais-rgb.xbws.org/viewtopic.php?f=8&t=94 |
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| Auteur: | MDelauney [ Lun Avr 18, 2011 12:11 am ] |
| Sujet du message: | Calculer Uo et la raison r? |
U5+U6+U7= -27 et U9= -15 Calculer Uo et la raison r. Jai commencé par faire U9= Uo + 9r = -15 |
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| Auteur: | ifetekil [ Lun Mai 30, 2011 12:13 am ] |
| Sujet du message: | Calculer Uo et la raison r? |
on a u0 + 9r = -15 u0 + 6r = -9 deux equa. deux inconnus : solution : r = -2 et U0= 3 |
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| Auteur: | wuwifegsah [ Lun Mai 30, 2011 6:09 am ] |
| Sujet du message: | Calculer Uo et la raison r? |
Suite artihmétique U5 + U6 + U7 <=> U0 + 5r + U0 + 6r + U0 + 7r = 3U0 + 18r = -27 <=> U0 + 6r = -9 U9= -15 <=> U0 + 9r = -15 Systme déquations deux inconnues : U0 + 6r = -9 U0 + 9r = -15 A toi de jouer ;) See ya |
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| Auteur: | AgobartA [ Lun Mai 30, 2011 11:25 am ] |
| Sujet du message: | Calculer Uo et la raison r? |
Bonjour, U(5) + U(6) + U(7) = -27 U(9) = -15 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Si ta suite est arithmétique: U(n) = U(0) + n.r U(5) + U(6) + U(7) = -27 U(0) + 5r + U(0) + 6r + U(0) + 7r = 3.U(0) + 18r = -27 U(0) + 6r = -9 U(9) = U(0) + 9r = -15 Do le systme: U(0) + 6r = -9 U(0) + 9r = -15 3r = -6 r = -2 U(0) = -9 - 6r = -9 + 12 = 3 Do la solution: U(0) = 3et r = -2 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Simplement, Dragon.Jade :-) |
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| Auteur: | CRye [ Ven Juin 03, 2011 7:59 pm ] |
| Sujet du message: | Calculer Uo et la raison r? |
Salut! Données : ------------------------------ U(5) + U(6) + U(7) = -27 ( 1) ------------------------------ U(9) = -15 On sait que : ------------------------------[U(5) +U(7)]/2 = U(6) ce qui donne ------------------------------- U(5) +U(7) = 2 U(6) ce qui donne ------------------------------ U(5) +U6)+U(7) = 3U(6) = -27 ce qui donne ------------------------------ U(6) = -27/3 ce qui donne ------------------------------ U(6) = -9 ce qui donne ----------------------------- U(o) + 6r = -9 (2) On sait que ----------------------------- U(9) = -15 ce qui donne ----------------------------- U(o) + 9r = -15 (3) Calcul de la raison r On pose ---------------------------- ( 3 ) - ( 2 ) ce qui donne ------------------------------ U(o) +9r - U(o) - 6r = 3r ce qui donne ------------------------------ 3r = -15 + 9 ce qui donne ----------------------------- 3r = - 6 ce qui donne ------------------------------- r = -6/3 ce qui donne ------------------------------- r = -2 Calcul de U(o) On sait : ------------------------------ U(6) = U(o) + 6r et ------------------------------- U(6) = -9 et ------------------------------- r = -2 ce qui donne ------------------------------- U(o) + 6(-2)= -9 ce qui donne ------------------------------ U(o) -12 = -9 ce qui donne ----------------------------- U(o = -9 +12 ce qui donne ----------------------------- U(o) = 3 Vérification ------------------------------ U(o) = 3 ------------------------------ r = -2 ---------------------------- U(5) = 3-10 ce qui donne ---------------------------- U(5) = -7 ---------------------------- U(6) = -9 ---------------------------- U(7) = 3 -14 ce qui donne ----------------------------- U(7) = -11 ce qui donne ---------------------------- U(5) +U(6)+ U(7) = -27 ce qui donne ---------------------------- -7 -9-11 = -27 ce qui donne ---------------------------- -27 = - 27 vrai ---------------------------- U(9) = -15 ce qui donne ----------------------------U(o) -9*2 = -15 ce qui donne ---------------------------- 3 -18 = -15 ce qui donne ---------------------------- -15=-15 vrai |
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