sachant que k (a + b) = k * a + k * b (formule de cours)
on aura
E = 9 * x + 9 * (-3) = 9x - 27
F = 4 * 5 + 4 * (-x) = 20 - 4x
G = 7 * x + 7 * (-8) = ... - ...
et H : vous avez compris
