Sagot :
a) 7x+3+5x+6 = 12x+9
b) -4y+9-5y-7 =-9y+2
c) 8a-9-12a+3 =-4a-6
d) 15b²+3b-9b²-5 = 6b²+3b-5
b) -4y+9-5y-7 =-9y+2
c) 8a-9-12a+3 =-4a-6
d) 15b²+3b-9b²-5 = 6b²+3b-5