B=(4x-9)/(3x+y)-(4y+9)/(3y+x) 
= [4x-(x-y)]/(3x+y) - [4y+(x-y)]/(3y+x) 
= (4x-x+y)/(3x+y) - (4y+x-y)/(3y+x) 
= (3x+y)/(3x+y) - (3y+x)/(3y+x) 
= 1 - 1 = 0

aaa... Ngầu quáNguyễn Thế Duy lm wen nha!!!

24

=> (x³+12):4= 57

=> x³+12=57.4

=> x³+12=228

=> x³=228-12

=> x³=216

=> x³=6³

=> x=6

Hay