a/ $\left(3x+5\right)^2=\left(3x+5\right)^4$
=> $3x+5\in \left\{0;1;-1\right\}$
*Trường hợp: 3x + 5 = 1
=> 3x = 1 - 5 = -4
=> $x=-\frac{4}{3}$
*Trường hợp 2: 3x + 5 = -1
=> 3x = -1 - 5 = -6
=> x = -6 : 3 = -2
*Trường hợp 3: 3x + 5 = 0
=> 3x = 0 - 5 = -5
=> $x=-\frac{5}{3}$
b/ $3^{2x+2}=81$
=> $3^{2x+2}=3^4$
=> $2x+2=4$
=> 2x = 4 - 2 = 2
=> x = 2 : 2 = 1
c/ $\left(5-2x\right)^3=125$
=> $\left(5-2x\right)^3=5^3$
=> $5-2x=5$
=> 2x = 5 - 5 = 0
=> x = 0 : 2 = 0
d/ $\left(x+2\right)^4=16$
=> $\left(x+2\right)^4=2^4$
=> x + 2 = 2
=> x = 2 - 2 = 0
