Bonsoir,
Résoudre en factorisant.
a)
(2x + 3)(x - 2) + 2(x - 2) = 0
(x - 2)(2x + 3 + 2) = 0
(x - 2)(2x + 5) = 0
→ Soit x - 2 = 0
x = 2
→ Soit 2x + 5 = 0
2x = -5
x = -2,5
S={ -2,5 ; 2 }
b)
25x² - 30x + 9 = 0
→ a² - 2ab + b² = (a - b)²
(5x - 3)² = 0
→ 5x - 3 = 0
5x = 3
x = 3/5 = 0,6
S={ 0,6 }
c)
(3x + 1)(5x - 1) - 4(5x - 1) = 0
(5x - 1)(3x + 1 - 4) = 0
(5x - 1)(3x - 3) = 0
→ Soit 5x - 1 = 0
5x = 1
x = 1/5 = 0,2
→ Soit 3x - 3 = 0
3x = 3
x = 1
S= { 0,2 ; 1 }
d)
(3x + 1)² - 49 = 0
(3x + 1)² - 7² = 0
a² - b² = (a - b)(a + b)
(3x + 1 - 7)(3x + 1 + 7) = 0
(3x - 6)(3x + 8) = 0
→ Soit 3x - 6 = 0
3x = 6
→ Soit 3x + 8 = 0
3x = -8
x = -8/3
S={ -8/3 ; 2}
Bonne soirée.
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Verified answer
Bonsoir,
Résoudre en factorisant.
a)
(2x + 3)(x - 2) + 2(x - 2) = 0
(x - 2)(2x + 3 + 2) = 0
(x - 2)(2x + 5) = 0
→ Soit x - 2 = 0
x = 2
→ Soit 2x + 5 = 0
2x = -5
x = -2,5
S={ -2,5 ; 2 }
b)
25x² - 30x + 9 = 0
→ a² - 2ab + b² = (a - b)²
(5x - 3)² = 0
→ 5x - 3 = 0
5x = 3
x = 3/5 = 0,6
S={ 0,6 }
c)
(3x + 1)(5x - 1) - 4(5x - 1) = 0
(5x - 1)(3x + 1 - 4) = 0
(5x - 1)(3x - 3) = 0
→ Soit 5x - 1 = 0
5x = 1
x = 1/5 = 0,2
→ Soit 3x - 3 = 0
3x = 3
x = 1
S= { 0,2 ; 1 }
d)
(3x + 1)² - 49 = 0
(3x + 1)² - 7² = 0
a² - b² = (a - b)(a + b)
(3x + 1 - 7)(3x + 1 + 7) = 0
(3x - 6)(3x + 8) = 0
→ Soit 3x - 6 = 0
3x = 6
x = 2
→ Soit 3x + 8 = 0
3x = -8
x = -8/3
S={ -8/3 ; 2}
Bonne soirée.