Distributivité: 2·(3 ± 4) = 2· 3 ± 2· 4

Go ! $x(x+1) = xx +1x = x^2 +x $   $-(a-b) = (-1)(a-b) =(-1)a -(-1)b = -a +b$   $(2+a)5 + 5(3-a) = 10+5a+15-5a = 25$ $2(ab+1)-(1+2ba) $ =   $-(-a+b) $ =