Tính: A= (-1/4 + 7/33-5/3)-9-15/12+6/11-48/49), B=1-1/2+2-2/3+3-3/4+4-1/4-3-1/3-2-1/2-1

A= (-1/4 + 7/33-5/3)-9-15/12+6/11-48/49) 
B=1-1/2+2-2/3+3-3/4+4-1/4-3-1/3-2-1/2-1
C=3/14:1/28-13/21:1/28+29/42:1/28-8
em cần gấp ạ