Ask your own question, for FREE!
Mathematics 13 Online
OpenStudy (smokeysthename):

@jim_thompson5910 mathhh

OpenStudy (smokeysthename):

jimthompson5910 (jim_thompson5910):

49x^2 + y^2 = 49 49x^2/49 + y^2/49 = 49/49 x^2 + (y^2)/49 = 1 (x-0)^2 + ((y-0)^2)/49 = 1 ((x-0)^2)/(1^2) + ((y-0)^2)/(7^2) = 1

jimthompson5910 (jim_thompson5910):

So this is an ellipse center: (0,0) Length of minor axis: 2*1 = 2 units Length of major axis: 2*7 = 14 units

jimthompson5910 (jim_thompson5910):

c^2 = a^2 - b^2 c^2 = 7^2 - 1^2 c^2 = 49 - 1 c^2 = 48 c = sqrt(48) c = 4*sqrt(3) This is the focal length

jimthompson5910 (jim_thompson5910):

So one focus is at ( 0, 4*sqrt(3) ) and another focus is at (0, -4*sqrt(3))

OpenStudy (smokeysthename):

thats long 0.0 lol okay lemme write this down and catch up on it :P

OpenStudy (smokeysthename):

okay i got it now..

jimthompson5910 (jim_thompson5910):

ok great

OpenStudy (smokeysthename):

jimthompson5910 (jim_thompson5910):

ok first we need the center

jimthompson5910 (jim_thompson5910):

how do we find this?

OpenStudy (smokeysthename):

uhmm, is it (0,0)?

jimthompson5910 (jim_thompson5910):

the two vertices are (2, 5) and (2, -5)

jimthompson5910 (jim_thompson5910):

the midpoint of this segment is ( (2+2)/2, (5+(-5))/2 ) = (2, 0)

jimthompson5910 (jim_thompson5910):

So the center is actually (2, 0)

OpenStudy (smokeysthename):

ohhh

jimthompson5910 (jim_thompson5910):

so (h,k) = (2, 0) ---> h = 2, k = 0

OpenStudy (smokeysthename):

okay got it

jimthompson5910 (jim_thompson5910):

the focal distance is 8 units since (2, 8) is 8 units from the center (2, 0)

jimthompson5910 (jim_thompson5910):

so c = 8

OpenStudy (smokeysthename):

alright. got that.

jimthompson5910 (jim_thompson5910):

a = 5 since 'a' is the distance from the center to either vertex

jimthompson5910 (jim_thompson5910):

a^2 + b^2 = c^2 5^2 + b^2 = 8^2 25 + b^2 = 64 b^2 = 64 - 25 b^2 = 39 b = sqrt(39)

jimthompson5910 (jim_thompson5910):

So we found this h = 2 k = 0 a = 5 b = sqrt(39)

OpenStudy (smokeysthename):

alright im following so far.

jimthompson5910 (jim_thompson5910):

plug all this info into ( (y-k)^2 )/(a^2) - ( (x-h)^2 )/(b^2) = 1

OpenStudy (smokeysthename):

do i need to find x and y?

jimthompson5910 (jim_thompson5910):

no

jimthompson5910 (jim_thompson5910):

those are variables that have no fixed value

OpenStudy (smokeysthename):

|dw:1365630292428:dw|

jimthompson5910 (jim_thompson5910):

good, and you can rewrite (y-0)^2 as just y^2, but that's optional

OpenStudy (smokeysthename):

okk cool (: i have 2 more

jimthompson5910 (jim_thompson5910):

ok

OpenStudy (smokeysthename):

OpenStudy (smokeysthename):

can you just quickly go through these cause i gotta go leave for work in 9 minutes.

jimthompson5910 (jim_thompson5910):

oh well we can do this later then

jimthompson5910 (jim_thompson5910):

I'm still tracking down the formulas we'll need

jimthompson5910 (jim_thompson5910):

sound good?

OpenStudy (smokeysthename):

nooo i gotta get this done :(

jimthompson5910 (jim_thompson5910):

ok

jimthompson5910 (jim_thompson5910):

Here's how I think it should be done, but don't have enough time to confirm

OpenStudy (smokeysthename):

no need to confirm. it'll be fine

jimthompson5910 (jim_thompson5910):

x + 5y^2 = 0 x = -5y^2 (x - 0) = -5(y-0)^2 (-1/5)(x - 0) = (y-0)^2 -4(1/20)(x - 0) = (y-0)^2 p = 1/20 ---> focal length is 1/20

jimthompson5910 (jim_thompson5910):

The vertex is (0,0) since h = 0 and k = 0

jimthompson5910 (jim_thompson5910):

The directrix is y = 1/20 since you add 1/20 to the x coordinate of the center

jimthompson5910 (jim_thompson5910):

Oh sorry, I meant to say x = 1/20 instead of y = 1/20

jimthompson5910 (jim_thompson5910):

The focus is (-1/20, 0) since you go 1/20 units to the left of the center

OpenStudy (smokeysthename):

okay makes sense.. last one

jimthompson5910 (jim_thompson5910):

how much time do we have?

OpenStudy (smokeysthename):

OpenStudy (smokeysthename):

about 5 minutes.

jimthompson5910 (jim_thompson5910):

ok then I'll make it quick

OpenStudy (smokeysthename):

kk

jimthompson5910 (jim_thompson5910):

multiply every term by the LCD 2x to get 3*2x = 6x (3/x)*2x = 6x/x = 6 (1/2)*2x = 2x/2 = x (1/x)*2x = 2x/x = 2 ------------------------------------------------------- So the expression simplifies to 6x - 6 ------ x - 2

OpenStudy (smokeysthename):

that makes sense!

OpenStudy (smokeysthename):

thank you!!!

jimthompson5910 (jim_thompson5910):

ok awesome, yw

OpenStudy (smokeysthename):

Off to work!! ttyl (:

jimthompson5910 (jim_thompson5910):

cya later

Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!
Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!