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Commutativité: 2·3 =3·2 ; 2+3 =3+2; 2-3 =-3+2 | 
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Go ! $2+ab+3-ba = 2+3+ab-ab = 5$ $a^2b+aba $ = $2xy+1-yx $ = $(1+a)^2-(-1+a+2)^2) $ = $b(1-a)+(a-1)b $ = $2(1+a)-(a+1)(1+1^2) $ =
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Commutativité: 2·3 =3·2 ; 2+3 =3+2; 2-3 =-3+2 |
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Go ! $2+ab+3-ba = 2+3+ab-ab = 5$ $a^2b+aba $ = $2xy+1-yx $ = $(1+a)^2-(-1+a+2)^2) $ = $b(1-a)+(a-1)b $ = $2(1+a)-(a+1)(1+1^2) $ =