[tex]\boxed{\log{xy}=\log{x}+\log{y}}[/tex]
[tex]\boxed{\log{\frac{x}{y}}=\log{x}-\log{y}}[/tex]
[tex]\boxed{\log{x^n}=n\log{x}}[/tex]
[tex]\log{2}=a\\ \log{3}=b\\ \log{5}=c[/tex]
a)
[tex]\log{\dfrac{3}{4}}=\log{3}-\log{2^2}=\log{3}-2\log{2}=\boxed{b-2a}[/tex]
b)
[tex]\log{900}=\log{(3^2\times10^2)}=2\log{3}-2\log{10}=\boxed{2(b-1)}[/tex]
