1°
3x(4x+1)+5(x+3) = 12x² + 3x + 5x + 15 = 12x² + 8x + 15

2°
7(2a-3b+1)-2(5a+6b-3) = 14a - 21b + 7 - 10a - 12b + 6 = 4a -33b + 13

3°
(3x-1)-(4x+5) = 3x - 1 - 4x - 5 = -x - 6

4°
7x(x-5)-(3x-1)(7x-3) = 7x² - 35x - 21x² + 9x + 7x - 3 = -14x² -19x - 3
---------------
a) 7xy-21x² = 7x(y-3x)

b) (4x-1)(7x+3)-2x(7x+3) = (7x+3)(4x-1-2x) = (7x+3)(2x-1)

c) (3x-5)(x-7)-(2x+1)(3x-5) = (3x-5)(x-7-2x-1) = (3x-5)(-x-8) = -(3x-5)(x+8)

d) (3x-1)²-7x(3x-1) = (3x-1)(3x-1-7x) = (3x-1)(-4x-1) = -(3x-1)(4x+1)

e) 5x-1+(7x-3)(5x-1) = (5x-1)(1+7x-3) = (5x-1)(7x-2)

f) 15a²b-10ab²+5ab = 5ab(3a - 2b + 1)
---------------
7*17-6*17+19*17 = 27*89 ???? c'est faux.
---------------

A=(2x-1)(x-7)-(x-7)(4x+3)

a) A = 2x²-14x-x+7-(4x²+3x-28x-21) = 2x²-14x-x+7-4x²+ 25x +21 = -2x²
+ 10x + 28

b) A = (x-7)(2x-1-4x-3) = (x-7)(-2x-4) = -2(x-7)(x+2)

c)
A(7) = 0  (par A = = -2(x-7)(x+2) )
A(0) = 28 (par A = -2x² + 10x + 28 )
----
Saud distraction - Vérifie tous les calculs.

Bonjour Pattrice


- Exercice 1 -
1.
3x(4x+1)+5(x+3)
= 12x² + 3x + 5x + 15
= 12x² + 8x + 15

2.
7(2a-3b+1)-2(5a+6b-3)
=14a-21b+7-10a-12b+6
=4a-33b+13

3.
(3x-1)-(4x+5)
=3x-1-4x-5
= -x - 6

4.
7x(x-5)-(3x-1)(7x-3)
= 7x²-35x-(21x²-9x-7x+3)
= 7x²-35x-21x²+9x+7x-3
= -14x²-19x-3


- Exercice 2 -
a) 7xy-21x²
= 7xy - 73 x²
= 7x(y - 3x)

b) (4x-1)(7x+3)-2x(7x+3)
= (7x+3)(4x-1-2x)
= (7x+3)(2x-1)

c) (3x-5)(x-7)-(2x+1)(3x-5)
= (3x-5)(x-7-(2x+1))
= (3x-5)(x-7-2x-1)
= (3x-5)(-x-8)

d) (3x-1)²-7x(3x-1)
= (3x-1)(3x-1-7x)
= (3x-1)(-4x-1)

e) 5x-1+(7x-3)(5x-1)
= (5x-1)(1+7x-3)
= (5x-1)(7x-2)

f) 15a²b-10ab²+5ab
= 5ab(3a-2b+1)



- Exercice 3 -
717-617+1917
= (7 - 6 + 19)17
= 20 17
= 340

(on a factorisé )



- Exercice 4 -
a) A=(2x-1)(x-7)-(x-7)(4x+3)
= 2x²-14x-x+7-(4x²+3x-28x-21)
= 2x²-15x + 7-4x²+25x+21
= -2x²+10x +28


b) A=(2x-1)(x-7)-(x-7)(4x+3)
A = (x - 7)(2x-1-(4x+3))
A = (x -7)(2x-1-4x-3)
A = (x-7)(-2x-4)
A = -2(x-7)(x+2)


c) Pour x = 7 :
A = -2(x-7)(x+2)
A = -2(7-7)(7+2)
A = 0


Pour x = 0 :
A = -2x²+10x +28
A = 28


A toi de tout vérifier, bon courage

Arf, je n'avais pas vu ta réponse J-P

No problemo