a) (2x+1)(6-x)-(2x+1)(5x+10)>0
(2x+1)(6-x-5x-10)<0
(2x+1)(-6x-4)<0
(2x+1)(3x+2)>0
tab de signes ⇒ S=]-∞;-2/3[ U ]-1/2;+∞[
b) (7-x)²-(6x+1)²≤0
(7-x+6x+1)(7-x-6x-1)≤0
(5x+8)(-7x+6)≤0
(5x+8)(7x-6)≥0
tab de signes ⇒ S=]-∞;-8/35] U [6/7;+∞[