1. Mar 5, 2010

stevecallaway

1. The problem statement, all variables and given/known data
.002x - .000001x^2 = .50

2. Relevant equations
-b+-sq.rt.((b^2)-(4ac))/2a

3. The attempt at a solution
Plugging a=-.000001, b=.002, and c=-.5 does not get the the correct answer. x is supposed to be 292.89. I can't remember any other way of going about trying to get this answer. Any suggestions?

2. Mar 5, 2010

elibj123

The formula is

( -b +- sqrt(b^2-4ac))/(2a)

3. Mar 5, 2010

Mentallic

As elibj123 said, the quadratic formula has a $\pm$ to consider. There are two solutions to any quadratic.

So you need to solve $$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$

You'll get your solution of 292.89 if you take $$x=\frac{-b-\sqrt{b^2-4ac}}{2a}$$

but you'll also get a solution of approx 1700 if you solve $$x=\frac{-b+\sqrt{b^2-4ac}}{2a}$$

Both solutions are correct, and you can check this by substituting your values of x back into the original equation .002x - .000001x^2 = .50
If your values of x are correct, the Left-hand side should approximately equal the right-hand side (depending on the approximation of your values of x).