Step-by-step explanation:
Inflection points are where a function changes concavity (the second derivative changes signs). At x = 4, f"(x) goes from negative to positive, so that's an inflection point. However, at x = 8, we don't know if f"(x) changes signs or not. So we can't say that that's an inflection point.
Question:
You are in a bike race. When you get to the first checkpoint, you are 2/5 of the distance to the second checkpoint. When you get to the second check point, you are 1/4 of the distance to the finish. If the entire race is 40 miles, what is the distance between the start and the first check point?
Answer: 4 miles
Step-by-step explanation:
Let distance between start to first checkpoint = x
First checkpoint to second checkpoint = 2/5 of x
Distance of start to checkpoint 1 = ( 2/5 of start to checkpoint 2)
Distance of start to checkpoint 2 = (1/4 of start to finish)
If start to checkpoint 2 = 1/4 of start to finish
Then,
Distance of start to checkpoint 1 = ( 2/5 * 1/4 of start to finish)
Distance of start to checkpoint 1 = 2/20 of start to finish = 1/10 of start to finish
Entire race = 40 miles = distance from start to finish
1/ 10 of 40
= ( 1/10) × 40
= 4 miles
I got -648 for the product
Answer: (D) 
Explanation:
Just a note on writing down these expressions: I recommend using parentheses whenever you can to avoid misinterpretation. An expression 1/x-1/y / 1/x+1/y could be interpreted by someone as 1/x-(1/y / 1/x)+1/y, which is a different thing.
An arc of length 30 m : l = 30 m.
r = 15 m, ∠ A = ?
Formula for the length of an arc is:
l = r π A / 180° ( where A is the central angle )
A = l · 180 / r π = ( 30 · 180 ) / ( 15 · 3.1415926 ) = 114.43 °
This is very close to your result.
