Bonjour,
a= 3/2 +5; b= -8/5 +3
2(3/2 +5)+ (-8/5 +3)= 6/2 +10+(-8/5 +3)= 13+(-8+3x5)/5= 13+(7/5)
= (13x5+7)/5= (65+7)/5= 72/5
5(3/2 +5)- (-8/5 +3)= 15/2+25+8/5-3= 15/2+8/5+22= (15x5+8x2+22x2x5)/10
= (75+16+220)/10= 311/10
2a= 13 déjà calculé voir en gras de la question 1
3(3/2 +5) / 2(3/2 +5)= (9/2+15) / 13= (9+15x2)/2) /13= 39/(2x13)= 39/26
= 3/2 simplifié par 13