Answer:

General Formulas and Concepts:
<u>Algebra I</u>
<u>Calculus</u>
Antiderivatives - integrals/Integration
Integration Constant C
U-Substitution
Integration Property [Multiplied Constant]: 
Trig Integration:
Step-by-step explanation:
<u>Step 1: Define</u>
<u />
<u />
<u />
<u>Step 2: Integrate Pt. 1</u>
- [Integral] Factor fraction denominator:

- [Integral] Integration Property - Multiplied Constant:

<u>Step 3: Identify Variables</u>
<em>Set up u-substitution for the arctan trig integration.</em>

<u>Step 4: Integrate Pt. 2</u>
- [Integral] Substitute u-du:

- [Integral] Trig Integration:
![\displaystyle \frac{1}{9}[\frac{1}{\frac{2}{3}}arctan(\frac{u}{\frac{2}{3}})] + C](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7B1%7D%7B9%7D%5B%5Cfrac%7B1%7D%7B%5Cfrac%7B2%7D%7B3%7D%7Darctan%28%5Cfrac%7Bu%7D%7B%5Cfrac%7B2%7D%7B3%7D%7D%29%5D%20%2B%20C)
- [Integral] Simplify:
![\displaystyle \frac{1}{9}[\frac{3}{2}arctan(\frac{3u}{2})] + C](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5Cfrac%7B1%7D%7B9%7D%5B%5Cfrac%7B3%7D%7B2%7Darctan%28%5Cfrac%7B3u%7D%7B2%7D%29%5D%20%2B%20C)
- [integral] Multiply:

- [Integral] Back-Substitute:

Topic: AP Calculus AB
Unit: Integrals - Arctrig
Book: College Calculus 10e
Answer:
-20 < 4 - 2x (subtract 4 from both sides)
-24 < -2x (divide each side by -2)
12> x (when you divide by a negative number, the inequality flips)
x< 12 ( I always put it so x is first)
so the answer is C
Let s = northbound train
Then
2s = southbound train
:
Distance = time * speed
4s + 4(2s) = 600
:
4s + 8s = 600
:
12s = 600
:
s = 600/12
:
s = 50 mph is the northbound train
Then
2(50) = 100 mph is the southbound train
:
:
Check:
4(50) + 4(100) = 600
The distance formula is:

We are given two points in the form (x,y), so plug in the values to the distance formula:

Next we can simplify. We know that 12-12 is 0, so we can drop it from the equation, as it will not affect our answer. Also, we know that -10-15 is -25:

The square and square root cancel each other out leaving us with 25.
The answer is 25.