# i'm absolutely terrible at math

• Jan 18th 2010, 09:06 AM
neilbachman
i'm absolutely terrible at math
so i somehow managed to get into business calculus in school and i'm sure these questions are easy for most but can u help.

Directions: Find the rate of change of the given function f(x) with respect to x for the prescribed value x=c
Question: f(x) = x- square root of x + 1/x^2 ; x=1

2. the manager of the many facets jewelry store models total sales by the function s(t)= 2,000t/ 4 + 0.3t where t is the time (years) since the year 2000 and s is measured in thousands of dollars.
a. At what rate are sales changing in the year 2002
b. what happens to sales in the "long run" (that is as t--> + infinity

3. an efficency study of the morning shift at a certain factory indicates that an average worker arriving on the job at 8:00 A.M. will have produced Q(t) = -t^3 + 8t^2 + 15t units t hours later.
a. compute the workers rate of production R(t) = Q(t)
b. at what rate is the workers rate of production changing with respect to time at 9:00 A.M.

4. Find the Limits
lim 5-2x^3/
x-->infinity x^2 +1

5. lim 2x^2 + x - 6/ 4x^2 -4x -3
x-->3/2

thanks for any help u can give.
• Jan 18th 2010, 09:11 AM
VonNemo19
Have you tried anything at all?
• Jan 18th 2010, 09:16 AM
neilbachman
yes i have but my answere are nowhere close on some and on the others, i have no clue where to even begin. i'm so lost
• Jan 18th 2010, 10:16 AM
Lord Darkin
Quote:

Originally Posted by neilbachman

5. lim 2x^2 + x - 6/ 4x^2 -4x -3
x-->3/2

Substitute 3/2 in for x.
• Jan 18th 2010, 10:22 AM
VonNemo19
Quote:

Originally Posted by neilbachman
so i somehow managed to get into business calculus in school and i'm sure these questions are easy for most but can u help.

Directions: Find the rate of change of the given function f(x) with respect to x for the prescribed value x=c
Question: f(x) = x- square root of x + 1/x^2 ; x=1

2. the manager of the many facets jewelry store models total sales by the function s(t)= 2,000t/ 4 + 0.3t where t is the time (years) since the year 2000 and s is measured in thousands of dollars.
a. At what rate are sales changing in the year 2002
b. what happens to sales in the "long run" (that is as t--> + infinity

3. an efficency study of the morning shift at a certain factory indicates that an average worker arriving on the job at 8:00 A.M. will have produced Q(t) = -t^3 + 8t^2 + 15t units t hours later.
a. compute the workers rate of production R(t) = Q(t)
b. at what rate is the workers rate of production changing with respect to time at 9:00 A.M.

4. Find the Limits
lim 5-2x^3/
x-->infinity x^2 +1

5. lim 2x^2 + x - 6/ 4x^2 -4x -3
x-->3/2

thanks for any help u can give.

For that first one, do you mean to say

$\displaystyle f(x)=x-\frac{\sqrt{x+1}}{x^2}$ with $\displaystyle x=1$ ?
• Jan 18th 2010, 03:02 PM
neilbachman
yes VONEMO19 except its square root of just x then plus 1 not square root of x+1
• Jan 18th 2010, 03:04 PM
neilbachman
Quote:

Originally Posted by Lord Darkin
Substitute 3/2 in for x.

ya i did that and it comes to 0 if u plug in 3/2 for x, so how do i simplify it or do something to be able to answer it
• Jan 18th 2010, 03:12 PM
VonNemo19
Quote:

Originally Posted by neilbachman
yes VONEMO19 except its square root of just x then plus 1 not square root of x+1

Do you think you could type it out just like you would input the funtion into your calculator?
• Jan 18th 2010, 03:15 PM
neilbachman
i dont know how to enter the equation using the symbols on the computer
• Jan 18th 2010, 03:17 PM
VonNemo19
Quote:

Originally Posted by neilbachman
i dont know how to enter the equation using the symbols on the computer

EG

If I wanted to write $\displaystyle y=x^2$ , I would type y=x^2.

If you want to make everything look super pretty....

Check out the pdf

http://www.mathhelpforum.com/math-he...-tutorial.html
• Jan 18th 2010, 03:20 PM
neilbachman
i seriously do not see them at least not on my keyboard
• Jan 18th 2010, 03:22 PM
VonNemo19
Quote:

Originally Posted by neilbachman
i seriously do not see them at least not on my keyboard

If you wanted to input $\displaystyle y=\frac{\sqrt{x+1}}{x^2}$ into your graphing calculator, how would you do it?
• Jan 18th 2010, 03:31 PM
neilbachman
oh gotcha, ya i can do it on my calculator, but not enter it on my computer like that, but how do u solve it
• Jan 18th 2010, 03:46 PM
skeeter
Quote:

Originally Posted by neilbachman
so i somehow managed to get into business calculus in school and i'm sure these questions are easy for most but can u help.

Directions: Find the rate of change of the given function f(x) with respect to x for the prescribed value x=c
Question: f(x) = x- square root of x + 1/x^2 ; x=1

$\displaystyle \textcolor{red}{f(x) = x - x^{\frac{1}{2}} + x^{-2}}$

use the power rule for derivatives to find f'(x), then evaluate f'(1)

2. the manager of the many facets jewelry store models total sales by the function s(t)= 2,000t/(4 + 0.3t) where t is the time (years) since the year 2000 and s is measured in thousands of dollars.
a. At what rate are sales changing in the year 2002

use the quotient rule to find s'(t), then evaluate s'(2)

b. what happens to sales in the "long run" (that is as t--> + infinity

what is the value for the horizontal asymptote for s(t) ?

3. an efficency study of the morning shift at a certain factory indicates that an average worker arriving on the job at 8:00 A.M. will have produced Q(t) = -t^3 + 8t^2 + 15t units t hours later.
a. compute the workers rate of production R(t) = Q(t) ???

should be R(t) = Q'(t). use the power rule to calculate Q'(t)

b. at what rate is the workers rate of production changing with respect to time at 9:00 A.M.

evaluate R'(1) = Q''(1)

4. Find the Limits
lim 5-2x^3/
x-->infinity x^2 +1

does not exist since degree of the numerator > degree of the denominator

5. lim 2x^2 + x - 6/ 4x^2 -4x -3
x-->3/2

factor numerator and denominator, cancel any common factors, then evaluate the limit at x = 3/2

...