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Mathematics 23 Online
zarkam21:

Help please

zarkam21:

1 attachment
zarkam21:

1 attachment
Vocaloid:

|dw:1519269250970:dw| compare this w/ your equation to determine the center (h,k)

zarkam21:

(-3,2)

Vocaloid:

(x-h)^2 = (x-2)^2 h = ?

zarkam21:

vertices are (2,0)(2,-6)

zarkam21:

-3

Vocaloid:

|dw:1519269470865:dw|

Vocaloid:

|dw:1519269476801:dw|

zarkam21:

+3

Vocaloid:

notice how (x-2) = (x-h) just comparing them side by side what do you think h might be equal to?

Vocaloid:

hint: subtract x from both sides

zarkam21:

-2?

Vocaloid:

almost -2 = -h h = ?

zarkam21:

2

Vocaloid:

good, let's repeat this process to find k (y-k)^2 = (y+1)^2 k = ?

zarkam21:

-1?

Vocaloid:

good so (h,k) = (2,-1) = your center

zarkam21:

was this part 3?

Vocaloid:

we are still on part I (the center.)

zarkam21:

oh okay

Vocaloid:

now, find the value of a by comparing the standard equation to the equation in the problem

Vocaloid:

|dw:1519270274987:dw|

Vocaloid:

compare these side by side, what's the value of a?

zarkam21:

36?

Vocaloid:

close but not quite a^2 = 36, a = ?

zarkam21:

6

Vocaloid:

good so the coordinates of the vertices are: (h+a,k), (h-a,k) plug in the h, a, and k values to get the coordinates

zarkam21:

(2,0)(2,-6)

Vocaloid:

h = 2 k = -1 a = 6 re-try your calculations.

zarkam21:

(8,-1)(-4,-1)

Vocaloid:

good for part III) we will need to calculate the value of b compare the equation in the problem w/ the standard form equation to find the value of b

Vocaloid:

(y+1)^2/25 = (y-k)^2/b^2 find b

Vocaloid:

if you just compare the denominators 25 = b^2 b = ?

zarkam21:

5

Vocaloid:

good now, we need to find c c^2 = a^2 - b^2 for ellipses c = ?

Vocaloid:

** should also mention, leave it in radical form

zarkam21:

(2,2)(2,-8)

zarkam21:

would this be the foci?

Vocaloid:

no

Vocaloid:

calculate c where c^2 = a^2 - b^2 as a reminder, we determined a to be 6 and b to be 5

zarkam21:

36-25=11^2=22

Vocaloid:

not sure where you're getting 22 from but yes, c^2 = 11 so c = sqrt(11) then the foci are just (h+c,k) and (h-c,k) so (2+sqrt(11), -1) and (2-sqrt(11),-1)

Vocaloid:

anyway, for IV we determined the vertices to be (8,-1)(-4,-1) major axis is along x, it's 2 * 6 = 12 units long minor axis is along y, it's 2 * 5 = 10 units long this should be sufficient to graph your ellipse

zarkam21:

so it would be (12,0) and (0,10)

Vocaloid:

no the ellipse is not centered at 0 12 and 10 are the lengths of the axes not the coordinates of the vertices.

Vocaloid:

create an ellipse with vertices (8,-1)(-4,-1), major axis length 12, minor axis length 10.

zarkam21:

would it just be the equation given

Vocaloid:

it is asking for a graph not an equation

Vocaloid:

|dw:1519272366586:dw|

Vocaloid:

|dw:1519272389968:dw|

Vocaloid:

|dw:1519272400272:dw|

Vocaloid:

using the information provided, graph the ellipse, labelling the vertices.

zarkam21:

1 attachment
Vocaloid:

check the minor axis again if the center is (2,-1) then the ellipse crosses (2,-1+5) and (2,-1-5) so (2,4) and (2,-6)

zarkam21:

1 attachment
Vocaloid:

good, that's about right

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