Is There a Way to Solve an Equation with One Unknown Using MATLAB?

[sara_87]

Homework Statement

i want to find the value of k in the following equation:
8.7-(0.75/k)=[e^(8k)](11.7-(0.75/k))

Homework Equations

The Attempt at a Solution

i know i can use MATLAB but i don't have MATLAB and i don't even know how to do it on matlab; does anyone know how to do it on matlab?
is there an alternative method to find k?

thank you

 

[Dick]

If you don't have any special tools, write the problem as f(k)=exp(8*k)*(11.7-.75/k)-(8.7-0.75/k). Now you want to find where f(k)=0. Now graph it and look for a zero, or just try different values of k until you find one where f(x) is positive and one where it's negative. E.g. f(0.03)<0 and f(0.04)>0. That means there is a root between 0.03 and 0.04. Try the midpoint k=0.035 and keep refining the interval containing the root until you get enough significant digits for the needs of the problem. This is called 'bisection'.

 

[sara_87]

yes i know that method but it takes too long and I'm lazy.
i just need the answer without the working out so i don't want to take too much time finding the value for k.

 

[cristo]

yes i know that method but it takes too long and I'm lazy.
i just need the answer without the working out so i don't want to take too much time finding the value for k.

Well, you should just probably wait until you get to a computer with maple or MATLAB or whatever. Otherwise, you'll need to do it the long way!

 

[HallsofIvy]

There is no simple formula for such a problem. You might be able use the Lambert W function, but I suspect just getting it into the right form for that would be much more work that the graph Dick suggested.

 

[sara_87]

yes but how do i type that into MATLAB and how do i find k using matlab? what do i type?

 

[EnumaElish]

Yahoo search "solving equations Matlab" results in http://www.mathworks.com/matlabcentral/newsreader/view_thread/157139 among others.

 

[HallsofIvy]

Yahoo search "solving equations Matlab" results in http://www.mathworks.com/matlabcentral/newsreader/view_thread/157139 among others.

In other words, there is NO "closed form" solution- it's not just a matter of "not knowing how to put it in".