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OrianeDragnir
@OrianeDragnir
May 2019
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Bonjour quelqu'un pourrait il m'aider pour ces équations svp ?
a) 9x + 2 = 3x - 4 ( j'ai trouvé x= -1 )
b) ( 2x + √5)² = 5 ( la j'ai pas trouvé)
c) x²- 16 = 0 (la j'ai pas trouvé non plus)
d) x² - 18x + 81 - 5 ( x - 9) = 0 ( la non plus j'ai pas trouvé)
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swnn
Verified answer
A) 9x+2 = 3x-4
9x-3x = -4-2
6x = -6
x = -6/6 = -1 → ok
b) (2x+√5)² = 5
(2x +√5)² - (√5)² = 0
cf 3 identité remarquable
donc
(2x+√5+√5)(2x+√5 -√5) = 0
(2x+2√5)*2x = 0
2x+2√5=0 ou 2x=0
2x = -2√5 ou x=0
x = (-2√5)/2
S = {(-2√5)/2;0}
c) x ²-16 = 0
x ² - 4 ² = 0
(x-4)(x+4) = 0
x-4=0 ou x+4=0
x=4 ou x=-4
S = {-4;4}
d) x²-18x+81 -5(x-9) = 0
(x-9)²-5(x-9)=0
(x-9)[(x-9)-5]=0
(x-9)(x-14) = 0
x-9=0 ou x-14=0
x=9 ou x=14
S={9;14}
1 votes
Thanks 1
OrianeDragnir
Merci beaucoup tu me sauve la vie !!!
isapaul
Verified answer
Bonjour,
a)
9x + 2 = 3x - 4
6x = - 6
x = -1
b)
(2x + √5)² = 5
4x² + 5 + 4√5x = 5
4x² + 4√5 x = 0
4x( x + √5) = 0 deux solutions soit x= 0 soit x = -√5
c)
x² - 16 = 0
(x - 4)(x + 4) = 0 deux solutions soit x= 4 soit x = -4
d)
x² - 18x + 81 = (x - 9)² donc
(x - 9)² - 5(x - 9) = 0
(x - 9)( x - 9 - 5 ) = 0
(x - 9)(x - 14) = 0 deux solutions soit x = 9 soit x = 14
Bonne journée
2 votes
Thanks 2
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Lista de comentários
Verified answer
A) 9x+2 = 3x-49x-3x = -4-2
6x = -6
x = -6/6 = -1 → ok
b) (2x+√5)² = 5
(2x +√5)² - (√5)² = 0
cf 3 identité remarquable
donc
(2x+√5+√5)(2x+√5 -√5) = 0
(2x+2√5)*2x = 0
2x+2√5=0 ou 2x=0
2x = -2√5 ou x=0
x = (-2√5)/2
S = {(-2√5)/2;0}
c) x ²-16 = 0
x ² - 4 ² = 0
(x-4)(x+4) = 0
x-4=0 ou x+4=0
x=4 ou x=-4
S = {-4;4}
d) x²-18x+81 -5(x-9) = 0
(x-9)²-5(x-9)=0
(x-9)[(x-9)-5]=0
(x-9)(x-14) = 0
x-9=0 ou x-14=0
x=9 ou x=14
S={9;14}
Verified answer
Bonjour,a)
9x + 2 = 3x - 4
6x = - 6
x = -1
b)
(2x + √5)² = 5
4x² + 5 + 4√5x = 5
4x² + 4√5 x = 0
4x( x + √5) = 0 deux solutions soit x= 0 soit x = -√5
c)
x² - 16 = 0
(x - 4)(x + 4) = 0 deux solutions soit x= 4 soit x = -4
d)
x² - 18x + 81 = (x - 9)² donc
(x - 9)² - 5(x - 9) = 0
(x - 9)( x - 9 - 5 ) = 0
(x - 9)(x - 14) = 0 deux solutions soit x = 9 soit x = 14
Bonne journée