Développer et réduire.... N= (4-3a) (a-5) + 15a S= (5+x) (x+4) + 3x (1-2x)

N= 4xa+4x(-5)+(-3a)xa+(-3a)x(-5)+15a
=4a-20+(-3)2+15a+15a
=34a-9-20 = 34a-29

N = (4-3a) (a-5) + 15a
N = 4a -20 -3a² +15a +15a
N = -3a²  +34a -20

S= (5+x) (x+4) + 3x (1-2x)
S = 5x +20 +x² +4x +3x -6x²
S = 5x² +12x +20