C) 3x(2x-12)=0
3x=0
x=0
2x-12=0
2x=12
x=12/2
x=6
D) (x-1)(x+9)=8x
x^2+9x-x-9=8x
x^2+8x-8x-9=0
x^2-9=0
(x-3)(x+3)=0
x-3=0
x=3
x+3=0
x=(-3)
Exercice 5
A) A=4x^2-12x+9-(2x^2+2x-3x-3)
A=4x^2-2x^2-12x-2x+3x+9+3
A=2x^2-11x+12
B) A=(2x-3)(2x-3-x-1)
A=(2x-3)(x-4)
C) x=(-5)
A=(2*(-5)-3)(-5-4)
A=(-10-3)(-9)
A=(-13)*(-9)
A=117
D) (2x-3)(x-4)=0
2x-3=0
2x=3
x=3/2
x-4=0
x=4
E) 2x^2-11x+12=12
2x^2-11x+12-12=0
2x^2-11x=0
x(2x-11)=0
x=0
2x-11=0
2x=11
x=11/2