Bonjour , je suis en 3 eme et j ai besoins d aide svp c est pour lundi : Exercice 1 On donne G=x²-10x+25+(x-5)(7-2x) 1) Développer et reduire G 2) Factoriser l'

1)
G = x^2 - 10x + 25 + x × 7 - 2x × x - 5 × 7 - 5 × (-2x)
= x^2 - 10x + 25 + 7x - 2x^2 - 35 + 10x
= - x^2 + 7x - 10

2) x × x - 2 × 5 × x + 5 × 5
= (x-5)^2

3) On sait que x^2 - 10x + 25 = (x-5)^2
Donc G = (x-5)(-x-2)

4) x × (-x) + x × 2 - 5 × (-x) - 5 × 2
= - x^2 + 2x + 5x - 10
= x^2 + 7x - 10

Ex2.
1) 7x+8 = 0
7x = -8
x = -8/7

2) 5-7x = -11
7x = 11 + 5
x = 16/7x

3) 4x-7 = 3x + 8
4x - 3x = 7 + 8
x = 15

4) 8 + (3x-2) = 5x - (3x-5)
8 + 3x - 2 = 5x - 3x + 5
6 + 3x = 2x + 5
3x - 2x = 5 - 6
x = -1

5) Soit ( x - 8 ) = 0, soit (7x - 7) = 0
Donc soit x = 8, soit x = 1

Exercice 1
1:
G=x2-10x+25+7x-2x2-35+10x
=-x2+7x-10
2:
X2-10x+25=(x-5)2
3:
G=(x-5)2+(x-5)(7-2x)
=((x-5)((x-5)(7-2x))
=(x-5)(-x+2)
4:
(X-5)(-x+2)=0
Si x-5=0 ou -x+2=0
X=5 ou x=2
Exercice 2
1:
7x+8=0
X=8/7
2: 
5-7x=-11
X=16/7
3:
4x-7=3x+8
X=15
4:
8+(3x-2)=5x-(3x-5)
6+3x=2x+5
X=-1
5:
(X-8)(7x-7)
X-8=0 ou 7x-7=0
X=8 ou x=1