Bonjour,
1) A = 25x² - 36 - (x-2) (5x + 6)
= 25x² - 36 - (5x² + 6x - 10x - 12)
= 25x² - 5x² - 6x + 10x - 36 + 12
= 20x² + 4x - 24
2) a² - b² = (a+b)(a-b)
donc : 25x² - 36 = (5x)² - 6² = (5x+6)(5x-6)
3) A = 25x² - 36 - (x-2) (5x + 6)
= (5x+6)(5x-6) - (x-2)(5x+6)
= (5x+6)[(5x-6)-(x-2)]
= (5x+6)(4x-4)
= 4(5x+6)(x-1)
4) a) x=0 ⇒ A = 20(0²) + 4(0) - 24 = -24
b) x=1 ⇒ A = 4(5(1)+6)(1-1) = 0
c) x=2 ⇒ A = 25(2²) - 36 - (2-2) (5(2) + 6)
= 100 - 36 - 0
= 64
Bonjour,
A = 25x² - 36 - (x-2) (5x + 6)
= 25x² -36 -(5x² +6x -10x -12)
=25x² -36 -5x² -6x +10x +12
= 20x² +4x -24
Développer et réduire A.
2) Factoriser 25x² - 36
= (5x-6) (5x+6)
identité remarquable
3) Factoriser A.
(5x-6) (5x+6)- (x-2) (5x + 6)
=( 5x+6) ( 5x-6 -x+2)
= (5x+6) ( 4x -4)
4) Calculer A pour:
a) x=0
20x² +4x -24
= 0+0-24
= -24
b)x= 1
20x² +4x -24
= 20 +4+-24
= 0
c) x= 2
20x² +4x -24
=20 *4 +4*2 -24
= 40 +8-24
= 24