2:
a: 45-x=22+9
=>45-x=31
=>x=45-31=14
b: \(84+\left(2x-3\right)=129\)
=>2x-3=129-84=45
=>2x=48
=>x=24
d: Đặt \(A=2+2^3+2^5+...+2^{2x+1}\)
=>\(4A=2^3+2^5+...+2^{2x+3}\)
=>\(3A=2^{2x+3}-2\)
=>\(A=\dfrac{2^{2x+3}-2}{3}\)
Theo đề, ta có: A=682
=>\(2^{2x+3}-2=682\cdot3=2046\)
=>\(2^{2x+3}=2048\)
=>2x+3=11
=>2x=8
=>x=4






