Production Word Problem - Thank you.

[moname]

Profit is T(x) and production and selling is x. Equation for profit, prod/selling is T(x) = 3x^2 + 240x - 1800.
How many appliances must be produced and sold for a profit of $3,000? The answr is 40 appliances. Have no clue as to how the number 40 was achieved.

Here's what I can figure out on my own so far:
1. 3000 = -3x^2 + 240x - 1800 =
2. 3000 + 1800 = -3x^2 + 240x - 1800 + 1800
3. 4800 = -3x^2 = 240x
4. 4800 = 3(x ) (x )

That's all, folks....Thanks so much for your help and patience.

 

[Denis]

3000 = -3x^2 + 240x - 1800

Where did the -3x^2 come from? Tat should be :
3000 = 3x^2 + 240x - 1800 ; so:
3x^2 + 240x - 4800 = 0 ; divide by 3:
x^2 + 80x - 1600 = 0

If you can't solve that, see your teacher...

 

[moname]

The -3x^2 is the formula, which I copied incorrectly by omitting the neg sign. The correct equation is:
T(x) = -3x^2 + 240x - 1800.

I think I can figure it out with your previous post. Thanks for your help.

 

[Denis]

Ya: x^2 + 80x - 1600 = 0 ain't as neat as x^2 - 80x + 1600 = 0 !