# Math Help - i swear i'm right but teacher's arguing with me, please help a wounded student )':

1. ## i swear i'm right but teacher's arguing with me, please help a wounded student )':

(a) At a small clothing company, the estimated cost function for producing a new line of jeans is C(x)=(x^2-7x+30)/x, where is the number of pairs of jeans produced, in thousands. is measured in dollars.
i) Calculate the cost of a pair of jeans at a production level of 3000 pairs.
ii) Determine the rate at which the cost is changing at a production level of 3000 pairs of jeans using any method. Show all work.

I got approx. $0.99 for the first one, and 1 for the second. She won't help me or give me the solution and i have a test in 2 periods! D: HELP? 2. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )' I can't see what your cost function is... 3. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )' i'm sorry! i guess it wouldn't let me submit the division bar i have on my word document! I edited it now, please help again 4. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )' For part i) you need to evaluate C(3), since x represents the number of thousands of pairs of jeans. For part ii) you need to evaluate C'(3), since C'(x) represents the rate of change of the cost for x-thousand pairs of jeans. 5. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )' OH oh my goodness how could i not realize that... i think once i copied it down on paper i left out the important details and just focused on the function. thank you so much :') so i) is$2
and ii) is -1.56?

6. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )'

Originally Posted by jenny85
OH oh my goodness how could i not realize that... i think once i copied it down on paper i left out the important details and just focused on the function. thank you so much :')

so i) is \$2
and ii) is -1.56?
I don't think [3^2 - 7(3) + 30]/3 is 2...

7. ## Re: i swear i'm right but teacher's arguing with me, please help a wounded student )'

Fundamental rule- your teacher is NOT arguing with you- you are arguing with your teacher!