Développer
A=25x²-16-3(5x-4)(x+6)
=25x²-16-3(5x²+26x-24)
=10x²-78x+56
Factoriser
A=25x²-16-3(5x-4)(x+6)
=(5x+4)(5x-4)-3(5x-4)(x+6)
=(5x-4)(5x+4-3(x+6))
=(5x-4)(2x-14)
=2(x-7)(5x-4)
Resoudre l equation A=0
A=0
(x-7)(5x-4)=0
x=7 ou x=4/5
Resoudre l'équation A=56
A=56
10x²-78x+56=56
10x²-78x=0
x(10x-78)=0
x=0 ou x=7,8
