Answer:
y = -1/10x^2 +2.5
Step-by-step explanation:
The distance from focus to directrix is twice the distance from focus to vertex. The focus-directrix distance is the difference in y-values:
-1 -4 = -5
So, the distance from focus to vertex is p = -5/2 = -2.5. This places the focus 2.5 units below the vertex. Then the vertex is at (h, k) = (0, -1) +(0, 2.5) = (0, 1.5).
The scale factor of the parabola is 1/(4p) = 1/(4(-2.5)) = -1/10. Then the equation of the parabola is ...
y = (1/(4p))(x -h) +k
y = -1/10x^2 +2.5
_____
You can check the graph by making sure the focus and directrix are the same distance from the parabola everywhere. Of course, if the vertex is halfway between focus and directrix, the distances are the same there. Another point that is usually easy to check is the point on the parabola that is even with the focus. It should be as far from the focus as it is from the directrix. In this parabola, the focus is 5 units from the directrix, and we see the points on the parabola at y=-1 are 5 units from the focus.
Answer:
22
74
Step-by-step explanation:
Answer:
B)
Step-by-step explanation:
Answer: A. 85.7
Step-by-step explanation:
Given : Two sections of a class took the same quiz.
Section A had 15 students who had a mean score of 80, and Section B had 20 students who had a mean score of 90.
We know that , 
Then , for section A :
Similarly in Section B, 
Total scores = Sum of scores in sec A+Sum of scores in sec B
=1200+1800=3000
Total students = Students in sec A +Students in sec B
=15+20=35
Now , the mean score for all of the students on the quiz =
Hence, the approximate mean score for all of the students on the quiz = 85.7
Thus , the correct answer is option A. 85.7.
Answer:
3.762 x 10^-7
Step-by-step explanation:
Alright this has the same exact concept as other scientific notation problems.
First, multiply your first numbers: 4.18 x 9 = 37.62
Next, we add our powers together -4 +-4 = -8 (can also be read as -4 - 4 = -8)
We now have 37.62 x 10^-8
Wait! This isn't in scientific notation.
Taking a closer look at this we see 37.62 x 10^-8 can be adjusted by moving the decimal over to the left. Scientific notation must be in simplest form with only one number on the left of the decimal. This gives up 3.762.
Now we need to adjust our notation. Since we moved the decimal over one we are adding one more power to our problem.
Our current power of -8 is now adding a power due to moving the decimal place over one unit to the left. This is equivalent to saying -8 + 1 which equals -7. Now that we fixed our powers, we can put our equation back together for our final answer
3.762 x 10^-7
