y = -3E-11x3 + 2E-07x2 + 3E-05x + 0.0077

I have the above equation and want to calculate x and so need to rearrange it:

x =

HELP!!

Why not use ^ to indicate powers? That is what SHIFT 6 is for.

I will use scientific notation instead of engineering notation:



or in engineering notation, as you have:



The two different methods are the same.

It is difficult to just solve for x. What is the y value? Do you have one? Are we to find the roots of the above cubic. That is, assuming y=0. That is the usual task.

Assuming y=0, then it has one real root and two complex roots.

The real one is 6.81884E3 or 6818.84

The two complex roots are

Does this help?

Also, we can do this with standard notation:



As you can see, just solving for x is a booger.:)

But, let me look at it and see what I can come up with. It may not be pleasant though.

Since the coefficient of x^3 is so small, we can probably disregard it and solve the resulting quadratic

That would probably be the best course of action. Is there more to the problem than what you have posted?

As a matter of fact, we can probably disregard the x^2 as well because it is small and solve the linear for x.

Doing that, we have



If we solve the quadratic for x, we get:



The cubic case is a monster. So, I would suggest the quadratic case since x^3 is so small.

You're welcome.