All categories

3 years ago

Equation for a parabola with a focus of (2, -2) and a directrix of y=-8

Mathematics

2 answers:

Komok [63]3 years ago

7 0

Y=1/8(x^2+4x+44) is correct

Fantom [35]3 years ago

5 0

Answer:

y=1/8(-x^2+4x+44

Step-by-step explanation:

In this question the given focus is (2,4) and a directrix of y = 8 and we have to derive the equation of the parabola.

Let (x,y) is a point on the given parabola.Then the distance between the point (x,y) to (2,4) and the distance from (x,y) to diractrix will be same.

Distance between (x,y) and (2,4)

= √(x-2)²+(y-4)²

And the distance between (x,y) and directrix y=8

= (y-8)

Now √(x-2)²+(y-4)² = (y-8)

(x-2)²+(y-4)² = (y-8)²

x²+4-4x+y²+16-8y = y²+64-16y

x²+20+y²-4x-8y = y²-16y+64

x²+20-4x-8y+16y-64=0

x²+8y-4x-44 = 0

8y = -x²+4x+44

You might be interested in

8) What is the area of parallelogram RSTU? *

Hatshy [7]

The answer is A. L*W which 4 by 6

7 0

2 years ago

Read 2 more answers

Find the surface area of square pyramid someone help

IgorC [24]

Answer:

65 square units

Step-by-step explanation:

The base of the pyramid is 5 by 5 , surface area is 25 square units.

the side of each one is 4 units "high" and 5 long at the base and to find the are of a triangle you multiple base times height then dived by 2. Therefore each side of the triangle is 10 units square. You have 4 sides so...

40 (total of all the sides ) +25 ( base ) = 65

4 0

2 years ago

Evaluate 4 times a number Q + 25 when Q equals 2

madam [21]

Answer:

4*(Q+25) Q=2

Step-by-step explanation:

4*(2+25) = 4*27 = 108

8 0

3 years ago

Which of the following is not one of the 8th roots of unity?

Anika [276]

Answer:

1+i

Step-by-step explanation:

To find the 8th roots of unity, you have to find the trigonometric form of unity.

1. Since $z=1=1+0\cdot i,$ then

$Rez=1,\\ \\Im z=0$

and

$|z|=\sqrt{1^2+0^2}=1,\\ \\\\\cos\varphi =\dfrac{Rez}{|z|}=\dfrac{1}{1}=1,\\ \\\sin\varphi =\dfrac{Imz}{|z|}=\dfrac{0}{1}=0.$

This gives you $\varphi=0.$

Thus,

$z=1\cdot(\cos 0+i\sin 0).$

2. The 8th roots can be calculated using following formula:

$\sqrt[8]{z}=\{\sqrt[8]{|z|} (\cos\dfrac{\varphi+2\pi k}{8}+i\sin \dfrac{\varphi+2\pi k}{8}), k=0,\ 1,\dots,7\}.$

Now

at k=0, $z_0=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 0}{8}+i\sin \dfrac{0+2\pi \cdot 0}{8})=1\cdot (1+0\cdot i)=1;$

at k=1, $z_1=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 1}{8}+i\sin \dfrac{0+2\pi \cdot 1}{8})=1\cdot (\dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2})=\dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2};$

at k=2, $z_2=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 2}{8}+i\sin \dfrac{0+2\pi \cdot 2}{8})=1\cdot (0+1\cdot i)=i;$

at k=3, $z_3=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 3}{8}+i\sin \dfrac{0+2\pi \cdot 3}{8})=1\cdot (-\dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2})=-\dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2};$

at k=4, $z_4=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 4}{8}+i\sin \dfrac{0+2\pi \cdot 4}{8})=1\cdot (-1+0\cdot i)=-1;$

at k=5, $z_5=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 5}{8}+i\sin \dfrac{0+2\pi \cdot 5}{8})=1\cdot (-\dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2})=-\dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2};$

at k=6, $z_6=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 6}{8}+i\sin \dfrac{0+2\pi \cdot 6}{8})=1\cdot (0-1\cdot i)=-i;$

at k=7, $z_7=\sqrt[8]{1} (\cos\dfrac{0+2\pi \cdot 7}{8}+i\sin \dfrac{0+2\pi \cdot 7}{8})=1\cdot (\dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2})=\dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2};$

The 8th roots are

$\{1,\ \dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2},\ i, -\dfrac{\sqrt{2}}{2}+i\dfrac{\sqrt{2}}{2},\ -1, -\dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2},\ -i,\ \dfrac{\sqrt{2}}{2}-i\dfrac{\sqrt{2}}{2}\}.$

Option C is icncorrect.

5 0

2 years ago

What's the answer to 1&2 plzz

Alexeev081 [22]

The first one is A. And Sowy but meh don't know the second one...

5 0

3 years ago