Répondre :
(3x+1)(7x-2) + 15+5
[3x * 7x + 3x * (-2)] + [1*7x + 1* (-2) ] + 15x + 5
21x² + (-6x) + 7x + (-2) +15x +5
21x² + 16x + 3
[3x * 7x + 3x * (-2)] + [1*7x + 1* (-2) ] + 15x + 5
21x² + (-6x) + 7x + (-2) +15x +5
21x² + 16x + 3