Logarithmic problem. Please help...

[BEAR737]

Hi all
I hope I'm in the right forum.
I am having real trouble with a logarithmic model. I have to find the equation of a logarithm in the form

f(x)=a+b ln(absolute value of x)

I have tried to graph this, so have swapped f(x) for y

The logarithm has to pass through points (25,30) and (60,60) on a graph, so I have two equations.

30=a+bln(25) and 60=a+bln(60)

This is as far as I got. I have to find the values of a. and b. but I'm just confused as to what to do after this point.
Sorry that my maths vocabulary isn't that great,
Any help would be so awesome and greatly appreciated.

Cheers

 

[stapel]

I have to find the equation of a logarithm in the form

f(x)=a+b ln(absolute value of x)

The logarithm has to pass through points (25,30) and (60,60) on a graph, so I have two equations.

30=a+bln(25) and 60=a+bln(60)

I have to find the values of a. and b.

You have two equations in two unknowns, so you can solve the system. A good start might be to solve each of the two equations for "a=", set the results equal to each other, and solve the linear equation for the value of "b". (Keep in mind that "ln(25)" and "ln(60)" are just numbers!) Then back-solve for "a".

 

[BEAR737]

You have two equations in two unknowns, so you can solve the system. A good start might be to solve each of the two equations for "a=", set the results equal to each other, and solve the linear equation for the value of "b". (Keep in mind that "ln(25)" and "ln(60)" are just numbers!) Then back-solve for "a".

Thanks stapel. This is a real help.