1)
M = 2/5 - 4/3 + 7/2 = 12/30 - 40/30 + 105/30 = 77/30
N = 2/3 - 5/3 × 3/2 = 2/3 - 5/1 × 1/2 = 2/3 - 5/2 = 4/6 - 15/6 = -11/6
L = (-7/4 + 1/2) : (2/7 + 1/4) = (-7/4 + 2/4) : (8/28 + 7/28) = -5/4 : 15/28 = -5/4 × 28/15 = -1/1 × 7/3 = -7/3
P = -28/5 : -21 = -28/5 × 1/21 = -4/5 × 1/3 = -4/15
2) L'inverse de M est 30/77 et l'opposé de N est 11/6
3) M - N = 77/30 - (-11/6) = 77/30 + 55/30 = 132/30 = 44/10 = 22/5
N × L = -11/6 × -7/3 = 77/18
M : N = 77/30 : -11/6 = 77/30 × -6/11 = 77/5 × -1/11 = -77/55
