Réponse :
Explications étape par étape
Bsr,
Je te fais la 1° colonne:
4x= 12
x=12/4 = 3
x-5 =15
x= 15+5 = 20
3x-7 =23
3x = 23-7 = 16
x= 16/3
5x-8 = -10
5x= -10+8 = -2
x= -2/5
-6x +3 =3x +15
3-15 = 3x+6x
-12 = 9x
-12/9 = x = -4/3
(3x-6) (2x+8) = 0
3x-6 = 0
=> 3x=6
x= 6/3 = 2
ou
2x+8 = 0
2x = -8
x= -8/2 = -4
(7x-8) - (3x-20) =0
7x-8 = 3x-20
7x-3x = -20+8
4x = -12
x = -12/4 = -3
(7x-8)( 3x-20) = 0
7x-8 = 0
7x = 8
x = 8/7
ou
3x-20 = 0
3x=20
x= 20/3
x² = 16
x= √16 = 4
x² = -100
impossible, un carré est toujours positif
4x² -2 = 24
4x² = 24+2 = 26
x² = 26/4 = 6,5
x = √6,5 =2,55
(3+x) ² = 100
(3+x) = 10
x= 10 -3 =7
☺
