Answer:
3 gallons per mile, slope of 3
Step-by-step explanation:
To find out how many gallons the train uses per mile, look at the point (50,150). If you know that the train used 150 gallons to travel 50 miles, do 150/50 to get an answer of 3 gallons per mile.
For the second part, you know that as x increases by 1 (miles traveled) y (gallons) increases by 3, so therefore the slope is 3. You can also check this value by plugging in the points (150,450) and (50,150) into the 
Answer:
2444
Step-by-step explanation:
The total cost is the integral of the marginal cost.

The total cost of producing units 144 through 625 is 2444.
_____
If all you need is a number, a graphing calculator can give you that.
The answer is $6.38 hope this helps
Answer: k=3
Step-by-step explanation:
To solve for k, you want to isolate k.
[add both sides by 8]
[multiply both sides by 5/2]
[subtract both sides by 35]
[divide both sides by 5]

Now, we know that k=3.
9x⁹ - 90x⁸ - 351x⁷
What do each of these numbers have in common?
They ALL have 9x⁷ in them!
So, divide each one of these by 9x⁷
9x⁹ ÷ 9x⁷ = 9x²
-90x⁸ ÷ 9x⁷ = -9x
-351x⁷ ÷ 9x⁷ = -39
So, factorized completely, it is :
9x² - 9x - 39
~Hope I helped!~