Giải các phương trình :
a) \(3^{x+4}+3.5^{x+3}=5^{x+4}+3^{x+3}\)
b) \(25^x-6.5^x+5=0\)
c) \(4.9^x+12^x-3.16^x=0\)
d) \(\log_7\left(x-1\right)\log_7x=\log_7x\)
e) \(\log_3x+\log_{\sqrt{3}}x+\log_{\dfrac{1}{3}}x=6\)
f) \(\log\dfrac{x+8}{x-1}=\log x\)