Si x-y = w, alors x-y+z = w+z, ça permet de simplifier la dernière colonne et de gagner du temps.
a.
1. x-y = 4.5 - (-1.5) = 5.5
2. x-y+z = 5.5 + 2 = 7.5
b.
1. x-y = -6 -(-5) = -1
2. x-y+z = -1 + 3.5 = 2.5
c.
1. x-y = 7 - (-5) = 12
2. x-y+z = 12 + (-4) = 8
d.
1. x-y = 1.5 - (-9) = 10.5
2. x-y+z = 10.5 + (-8) = 2.5
e.
1. x-y = 7 - (-6) = 13
2. x-y+z = 13 + 9.5 = 22.5
