1 ) Développer
E = 5(x-1) (x+2) - (x+2)² + 3(x+5)
E = (5x - 5) (x+2) - (x² + 4x + 4) + 3x + 15
E = 5x² + 10x - 5x - 10 - x² - 4x - 4 + 3x + 15
E = 4x² + 4x + 5
2) Factoriser
E = 4x² + 4x + 5
E = x(x² +4 - 5/x)
3) F = 9x² - E
F = 9x² - 4x² + 4x + 5
F = 5x² + 4x + 5
F = (5x + 1) (x-1)
4)
a) (5 * -2/5 +1) (-2/5 -1)
=( -10/5 + 5/5 ) (-2/5 - 5/5)
=(-5/5) (-7/5)
=35/5= 7
F = 0
(5x+1)(x-1) = 0
Soit 5x+1 = 0
donc 5x = -1 ----> x = -1/5
Soit x-1 = 0 ----> x = 1
