[tex]bonjour\\\\\\M = 3 x² + 15 x - 3 x^{2} - 4 x - 15 x - 20 \\M = - 4 x - 20 \\\\N = 8 x^{2} - 2 x - 4 x + 1 - 8 x^{2} + 13 x\\N = 7 x + 1 \\\\M = ( x + 5 ) ( 3 x - 3 x - 4 ) \\M = ( x + 5 ) ( - 4 ) \\\\\\\\\\\\[/tex]
premier jour = x km
second = x - 10
troisième = 2 ( x - 10 ) = 2 x - 20
x + x - 10 + 2 x - 20 = 100
4 x = 100 + 30
4 x = 130
x = 32.5
jour 1 = 32.5 km
jour 2 = 22.5 km
jour 3 = 45 km