Can anyone help me with a quadratics equation?

[SheWhoWaits]

Okay, this was a word problem and we got it down to this equation:
-x^2+820x-44800=0 If you multiply the whole thing by -1 you get: x^2-820x+44800=0 So if you use the quadratic formula on either equation, you should get the same answer, right? Yet we've done both equations several times, and the answers are different. Why? What is wrong with our reasoning?

[kiana]

Nothing is wrong with your reasoning, you may have erred on your use of the quadratic formula. Common errors could include forgetting that -b is positive if b is negative, that -4ac is negative if a and c are both negative, that 2a is negative if a is negative, or that b^2 is always positive. Without knowing what answers you got, it's impossible to trace further.

ETA: Unless I mistyped, you should get 410 +/- 30 sqrt 137, which are about 761 and 59

[SheWhoWaits]

That's the answer we get when we solve the 2nd equation, but for some reason, the first one comes out to ca. -51 and 871. Any way you can figure out what we did wrong?

[SheWhoWaits]

That's it! We used positive 4ac, forgetting that we had 3 negatives there instead of 2. Thanks. Now it works.