Help with a couple derivatives?

[itsweird182]

I am having trouble finding the derivative of these two functions. If anyone could tell me what they are and walk me through it it would be greatly appreciated!

#1) R = 1500x + 3000(2x+3)^1-1000

#2) P = 200,000/(q+1)^2

 

[tkhunny]

I rather have trouble beliving the first. Please try again and be more careful with notation.

For the second, it may help to see that:
P = 200000 * (q+1)^(-2)

 

[itsweird182]

I rather have trouble beliving the first. Please try again and be more careful with notation.

For the second, it may help to see that:
P = 200000 * (q+1)^(-2)

I'm not sure what you're saying about the first one? That is exactly how it looks in the book. Also, I actually figured out how to do that one. I got 1500-6000/(2x+3)^-2 for the answer on that one.

For the second one, I got -400000q/(q+1)^3 but I don't think thats right because when I plug 49 into that, I get -156.8 and in the book it says I should get -3.20. What did I do wrong?

 

[tkhunny]

1) I do not believe it. For starters, it is VERY unlikely that your book used the "^" for exponentiation. Next, do you really expect me to believe that the author WROTE and exponent of 1? Here's what you have written shoudl look like in a book. \(\displaystyle R = 1500x + 3000(2x+3)^{1}-1000\) If it does not look like that in your book, then you need to try again. Perhaps you mean this: \(\displaystyle R = 1500x + 3000(2x+3)^{-1}-1000\) This ALMOST leads to your answer. How did the multiplication turn into division? Are you sure you are clear on how to handle negative exponents, whether they be in the numerator or the denominator?

2) How did you get a "q" in the numerator? (d/dx)(q+1) = 1, not q.

 

[mmm4444bot]

I'm not sure what you're saying about the first one?

He's saying that you should proofread your typing. You typed a linear function; your R's derivative is 7500 because that's the slope of the line.

That is exactly how it looks in the book.

No reputable math text generally and explicitly displays exponents of positive one.

Also, I actually figured out how to do that one. I got 1500-6000/(2x+3)^-2 for the answer on that one.

Not even close, using R as typed.

For the second one, I got -400000q/(q+1)^3 There is no factor of q in the numerator.