Maths 20 Pts exercice 57

A-(4-5x)(2x+3)-(4-5x) (10+x)
= (8x+12-10x²-15x)-( 40+4x-50x-5x²)
8x+12-10x²-15x-40-4x+50x+5x²
f=39x-28-5x²
B-
(4-5x)(2x+3)-(4-5x) (10+x)
= (4-5x)[(2x+3)-(10+x)]
=(4-5x)(x-7)