b)
[tex]\it log_{\frac{1}{2}}4= \dfrac{log_2 4}{log_2{\dfrac{1}{2}}} =\dfrac{log_22^2}{log_22^{-1}} =\dfrac{2}{-1} = -2
[/tex]
[tex]\it log_8 1024 = \dfrac{log_21024}{log_28} =\dfrac{log_2 2^{10}}{log_22^3} = \dfrac{10}{3}[/tex]
[tex]\it-2+\dfrac{10}{3} = \dfrac{-6+10}{3} =\dfrac{4}{3}\ .[/tex]
c)
[tex]\it \log_42 = log_4\sqrt4 = log_4 4^{\dfrac{1}{2}} = \dfrac{1}{2}\cdot log_4 4 = \dfrac{1}{2}[/tex]