1:
=>|2x+5|(1/4+1/2)=0
=>|2x+5|=0
=>2x+5=0
=>x=-5/2
2: A=2(1+2)+2^3(1+2)+...+2^59(1+2)
=3*(2+2^3+...+2^59) chia hết cho 3
A=2(1+2+2^2)+2^4(1+2+2^2)+...+2^58(1+2+2^2)
=7(2+2^4+...+2^58) chia hết cho 7
A chia hết cho 3
A chia hết cho 7
=>A chia hết cho BCNN(3;7)=21