bonjour
A = 2/3 - 2/3 x 9 /5
A = 2/3 - 18/15
A = 10/15 - 18/15 = - 8/15
B = ( 1 /6 - 1 /3 ) : ( 2/5 x 3 /4 )
B = ( 1/6 - 2 /6 ) : ( 6/20 )
B = - 1/6 x 20 /6
B = - 20 / 36
B = - 5 / 9
B - A = - 5 /9 - ( - 8 /15 ) = - 25/45 + 24/45 = - 1 /45
AB = - 8/15 x - 5 /9 = 40/135 = 8 / 27
A/B = - 8/15 x - 9 /5 = 72/75 = 24/ 25
somme de A et inverse de B = - 8/15 + ( - 9/5 ) = - 8/15 - 9/5 = - 8/15 - 27/15
= - 35/15 = - 7/3
produit de B par opposé de A = - 5/9 x 8/15 = - 40 /135 = - 8 /27
