Answer:
a
Step-by-step explanation:
A = first piece, b = second piece, c = third piece
a + b + c = 47
b = 3a
c = 5a + 2
a + (3a) + (5a + 2) = 47.....combine like terms
9a + 2 = 47
9a = 47 - 2
9a = 45
a = 45/9
a = 5 ft
b = 3a.....b = 3(5)....b = 15 ft
c = 5a + 2....c = 5(5) + 2.....c = 25 + 2....c = 27 ft
longest piece (c) = 27 ft
Answer:
1.778 times more or 16/9 times more
Step-by-step explanation:
Given:
- Mirror 1: D_1 = 8''
- Mirror 2: D_2 = 6"
Find:
Compare the light gathering power of an 8" primary mirror with a 6" primary mirror. The 8" mirror has how much light gathering power?
Solution:
- The light gathering power of a mirror (LGP) is proportional to the Area of the objects:
LGP ∝ A
- Whereas, Area is proportional to the squared of the diameter i.e an area of a circle:
A ∝ D^2
- Hence, LGP ∝ D^2
- Now compare the two diameters given:
LGP_1 ∝ (D_1)^2
LGP ∝ (D_2)^2
- Take a ratio of both:
LGP_1/LGP_2 ∝ (D_1)^2 / (D_2)^2
- Plug in the values:
LGP_1/LGP_2 ∝ (8)^2 / (6)^2
- Compute: LGP_1/LGP_2 ∝ 16/9 ≅ 1.778 times more
ANSWER
EXPLANATION
Since the directrix is
the axis of symmetry of the parabola is parallel to the y-axis.
Again, the focus being,
also means that the parabola will open upwards.
The equation of parabola with such properties is given by,
where
is the vertex of the parabola.
The directrix and the axis of symmetry of the parabola will intersect at
The vertex is the midpoint of the focus and the point of intersection of the axis of the parabola and the directrix.
This implies that,
and
The equation of the parabola now becomes,
Thus, the distance between the vertex and the directrix.
This means that,
Since the parabola opens up, we choose
Our equation now becomes,
This simplifies to
or
This is the same as,
The correct answer is D .