Bonjour,
A=x*(5x+12)+9-2*(4x*x+1)-3x
= 5x² +12x +9 -8x² -2-3x
= -3x² +8x +7
B=7*x*x*x-2-4x+19-3*x³+2x²+2+3x
= 7x³ -2 -4x +19 -3x³+2x² +2 +3x
= 4x³ +2x² -x +19
2)Calculer A et B pour x = 3
-3x² +8x +7
= -3*3² +8*3 +7
= -27 +24 +7
= 4
4*3³ +2*3² -3+19
= 4*27 +18 -3+19
= 108 +34
= 142
