Answer:
56.
Step-by-step explanation:
That is the number of permutations of 2 from 8
= 8P2
= 8!/(8-2)!
= 8!/6!
= 8 * 7
= 56.
Answer:
The equation of the parabola is 
.
Step-by-step explanation:
Since the directrix is of the form 
, the parabola is vertical. The vertex of the parabola (
) is the midpoint between the focus (
) and a point of the directrix (
), that is to say:
(1)
If we know that 
and 
, then the coordinates of the vertex of the parabola:
The vertex factor (
) is the distance of the focus with respect to the vertex:
![p = \sqrt{[F(x,y)-V(x,y)]\,\bullet \,[F(x,y)-V(x,y)]}](https://tex.z-dn.net/?f=p%20%3D%20%5Csqrt%7B%5BF%28x%2Cy%29-V%28x%2Cy%29%5D%5C%2C%5Cbullet%20%5C%2C%5BF%28x%2Cy%29-V%28x%2Cy%29%5D%7D)
(2)
If we know that and , then the vertex factor is:
The equation of the parabola in the vertex form is described below:
(3)
Where:
- Independent variable.
- Dependent variable.
- Coordinates of the vertex.
If we know that 
and , then the equation of the parabola is .
Answer:
18
Step-by-step explanation:
You can see from the table that 2 bracelets are made every 30 minutes.
There are 9 intervals of 30 minutes each in 4.5 hours.
So, the number of bracelets that are made in 4.5 hours is
9x2=18
Another way to see this is to note from the table that 4 bracelets are made in 60 minute, which is 1 hour. So, in 4 hours, 16 bracelets will be made. Also, from the table, 2 bracelets are made in 30 minutes, which is 1/2 hour. So, adding up, 18 bracelets are made in 4.5 hours.
