Question

What is the equation, and how can you tell?

Answer 1

(a) y=10^-x
(b) y=-10^x
(c) y=10^x
(d) y= -log(10)^x
(e) y=log(10)^x

Answer 2

\[y=\log x\]

Answer 3

Looks like a standard logarithm, however it is only on one side of the x axis and it should really be both, but I know it's none of the others so I'd say its \[y=\log_{10}(x)\] And to be honest, you only know these things by imagining how the plots look like and from experience. Although here you would need the function to "work" at the point (0,1) which whittles it down a touch.