Bonjour !
A : (3x -4) (7x+ 9) = 0 EPN
3x - 4 = 0 ou 7x + 9 = 0
3x = 4 ou 7x = -9
x = 4/3 ou x = -9/7
S = { -9/7 ; 4/3}
B : (x + 3)(-4x + 1) - (x + 3) (-3x + 4) = 0
<=> (x + 3)(-4x + 1 - (-3x + 4)) = 0
<=> (x + 3)(-4x + 1 + 3x - 4) = 0
<=> (x + 3)(-x - 3) = 0 EPN
x+3 = 0 ou -x -3 = 0
x = -3 ou x = -3
S = {-3}
C : 49x² = 144
<=> 49x² - 144 = 0
<=> (7x - 12)(7x + 12) = 0 EPN
7x - 12 = 0 ou 7x + 12 = 0
7x = 12 ou 7x = -12
x = 12/7 ou x = -12/7
S = {-12/7 ; 12/7}
D : (-6x + 7) = 64
<=> -6x = 64 - 7
<=> -6x = 57
<=> 6x = -57
<=> x = -57/6
<=> x = -19/2
S = {-19/2}
Voilà !
