Bonjour
1) 4 + 5 + x + x + x = 9 + 3x
2) 3(3+x)
3) si x = 2
3*3 + 3*2 = 9 + 6 = 15
bonus: (2x+1)(x-4)
= 2x² -8x + x -4
= 2x² -7x -4
