Thread: Graphing log Function

Graph
y=log base 3 (x+7)
It asks to graph, but i am just having problem solving for points(Y)

I know that you can also graph this function in exponential form
3^y=x+7

however, i tried to substitute in for x in the log function, but getting wrong answers
x=-7
y=log base 3(-7+7) = 1

expo
x=-6
3^y=-6+7
3^y=1
y=1

I am substituting different numbers for x but getting same answer, in fact the -6 is correct not the -7.

How do i find y in a using the log function?

Thank You

Originally Posted by hovermet

Graph
y=log base 3 (x+7)
It asks to graph, but i am just having problem solving for points(Y)

I know that you can also graph this function in exponential form
3^y=x+7

however, i tried to substitute in for x in the log function, but getting wrong answers
x=-7
y=log base 3(-7+7) = 1 <<<<<< log(0) is not defined!

...

If you don't want to use a calculator you should get powers of 3 as argument of the log function:


Therefore:






If you are allowed to use a calculator use the base-change-formula to get the y-values for any x > 7: