Question

The total cost of producing a type of tractor is given by C(x)=11000−20x+0.02x2, where x is the number of tractors produced. How many tractors should be produced to incur minimum cost?

Answer 1

Explanation:

You need to complete the square.

C(x) = 0.02(x^2 - 1000x ...) + 11000

C(x) = 0.02 (x^2 - 1000x + 500^2) + 11000 - 5000

C(x) = 0.02 (x^2 - 1000x + 500^2) + 6000

C(x) = 0.02(x - 500)^2 + 6000

Now if you look at the answer you will find that the square is completed. That means that number of tractors you could produce is 500 at a cost of 6000

There is a flow to this question that you may have trouble understanding.

First of all the 500^2. That comes from taking 1/2 of 1000 and squaring it. That's what you need to complete the square.

Bur that is not what you have adding into the equation. Remember that there is a 0.02 in front of the brackets.

500^2 = 250000

0.02 * 250000 = 5000

So that number must be subtracted to make the square = 0. When you remove the brackets, you should get 11000 all in all.

So what you have outside the brackets is 11000 - 5000 = 6000

The rest is just standard for completing the square.