Thread: graphs of logs

im having a bit trouble graphing logs. how do i know the shape of the graph? i know it passes through the points (1,0) along the x-axis. it goes down along the origin and what about the otherside thats going up?

like log₂ is diff from log₃ and is diff from log₆. is there rule?

sorry my terminology is all skewed, but, do u understand what im saying?

thanks!

Originally Posted by noork85

im having a bit trouble graphing logs. how do i know the shape of the graph? i know it passes through the points (1,0) along the x-axis. it goes down along the origin and what about the otherside thats going up?

like log₂ is diff from log₃ and is diff from log₆. is there rule?

sorry my terminology is all skewed, but, do u understand what im saying?

thanks!

Logarithms are inverse functions to exponentials, and exponentials are much easier to picture and graph than logarithms. So a good strategy is to graph the inverse function, then reflect it in the line y = x.

so lets say i have log₆(x+2) what should i do first? other than knowing that my graph passes through (1,0) and theres a horizontal shift of two to the left, i duno whats going on with my graph...but then that says alot, right? i know where graph goes along the neg y-axis (downwards), but what about along the positive y-axis?

Originally Posted by noork85

so lets say i have log₆(x+2) what should i do first? other than knowing that my graph passes through (1,0) and theres a horizontal shift of two to the left, i duno whats going on with my graph...but then that says alot, right? i know where graph goes along the neg y-axis (downwards), but what about along the positive y-axis?

I would do this...



So graph , then reflect it in the line .

oh, i see. okay ill do that too then. im not comfortable with a calculator yet so doing it by hand is my only option. thank u very much. will try it out and update how it goes.