# Thread: need to solve for x

1. ## need to solve for x

$\displaystyle 1.67*10^{-9}=.01x+.4x^2+4x^3$

2. Using a calc, the answer is:

$\displaystyle x\approx 1.670 \times 10^{-7}$

I don't think you can solve this one by hand...

3. What did you type into the calculator to get that answer? I guess I should have said that I already knew the answer since it was in the back of the book but I have no idea how to get the answer.

4. I have a CAS calculator (Casspad 330), so I just typed in the equation to solve.

You can also go here Wolfram|Alpha and type in:

solve 1.67*10^{-9}=0.01x+0.4x^2+4x^3

5. Originally Posted by Stroodle
I have a CAS calculator (Casspad 330), so I just typed in the equation to solve.

You can also go here Wolfram|Alpha and type in:

solve 1.67*10^{-9}=0.01x+0.4x^2+4x^3
okay thanks but I doubt they would put a problem in a book that you couldnt solve with at least a basic ti-XX graphing calculator. There has to be some way to do it on paper.

6. Yeah, I'm sure you can do it with a TI too. Unfortunately I can't remember how to use one... Have you tried plotting the graph on it?

I really don't know how you would find the solution without a calc - without a stupendous amount of trial and error..