Question

how do i graph these?

Answer 1

Just change the base of the first equation and the last two using the change of base formula. You use use either the natural log or log base 10 as the new base.

\[y=\log_{10} x/\log_{10}0.3 \]
The other two equations are all ready in log base 10.

Answer 2

but how to you graph them

Answer 3

Log a / Log b = log (a-b).
So, y = log(x-0.3) to base 10.

Now, you use different values of x and calculate the values of y using a calculator. Plot these points (x,y) on a coordinate graph. Then, draw a curve through them.

Remember, log of a negative number is not defined. So, x in this case must be at least 0.3.

Answer 4

What are you using, graphing calculator, geogebra, or by hand?

If you are using geobebra, just type the equation on the input line like this;

y=lg(x)/lg(0.3) make sure you use the parentheses

. http://www.geogebra.org/cms/

If you are doing the graph by hand, just pick a few values for x and then solve for y. Plot the (x,y) values that you get on graph paper.

If you are using a graphing calculator, then you will have to consult your manual on how to graph logarithms.

Note you can also change the equations into exponent form.

For example. \[f(x)= \log_{0.3}x \] becomes\[x=0.3^{y}\]

http://www.youtube.com/watch?v=6bBBs3FbLBM