 # Calculus Homework Assignment Anonymous
timer Asked: Feb 9th, 2019
account_balance_wallet \$9.99

### Question Description

There is a total of 9 questions that I need help with. 4 that I partially answered and 5 that I need help with understanding how to complete the problem. One has to do with finding the equation of a tangent line, one has to do with l'Hospital's rule, one has to do with approximating cost, one has to do with velocity, and multiple have to do with marginal cost/profit/revenue. If you need more time to given me explainations that's okay, I just need the answer within the time limit.

## Tutor Answer

KatS
School: Rice University   Attached are the solutions. Please let me know if you have any questions or if there are any errors.

Start by finding the derivative of the function:
f(x) = 5x^-2
f'(x) = 5*-2x^-3 = -10/x^3
Evaluate the function and the derivative at the point x = 1
f(1) = 5/1^2 = 5
f'(1) = -10/1^3 = -10
f'(1) will be the slope of the tangent line.
Use point slope form to develop the equation for the tangent line
y – y1 = m(x – x1)
y – 5 = -10(x-1)
y -5 = -10x + 10
y = -10x + 15

Evaluating at negative infinity would give you a indeterminate form. Take the derivative of the
top and bottom by applying l'hopitals
lim(x--> - inf) 14x + 10 / 12x – 5
Evaluating this limit at negative infinity would still give you in indeterminate form of – infinity / infinity. That means you should apply l'hopitals rule one more time
lim(x--> -inf) 14 / 12 = 14/12 = 7/6
The limit is 7/6

P'(4) was equal to 35. If t = 4, that means the year would be 2000 + 4 = 2004.
The rate would be 35000. Remember P is in thousands of dollars, so 35 really means 35000
Box 1: 35000
Box 2: 2004

Start with s(t) and set that equal to zero. That will tell you the time when the rock reaches the
ground
0 = 400 – 16t^2
16t^2 = 400
t^2 = 25
t=+-5
Since you cannot use a negative time, you should focus on the t = 5
Now you also needs to find the velocity at that time by plugging t = 5 into your derivative
equation.
S'(5) = -32*5 = -160 ft / sec
Box 1: - 160
Box 2: 5

The revenue function can be fo...

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