Conics (1 Viewer)

[joesmith1975]

Can't figure out x^2 + 16y^2 =25
Sketch it showing features.

Thanks in advance

 

[haboozin]

Can't figure out x^2 + 16y^2 =25
Sketch it showing features.

Thanks in advance

.

i think your really missing the point of sketching...
always go back to your definitions.
it could be an easy 4 mark Q in Q3 or so..

X^2 + 16y^2 = 25
is the same as

X^2/25 + Y^216/25 = 1

and by your definitions...

b^2 = a^2(1-e^2)

as trev said in other post since a>b
F = (+-ae,0)
and D is
x = +-a/e

incase you are not sure a would be 5 and b would be 5/4

 

[joesmith1975]

yere but what does e come out to be thats were im having trouble

 

[Mountain.Dew]

yere but what does e come out to be thats were im having trouble

x^2 + 16y^2 =25 ==> X^2/25 + Y^2(16/25) = 1 [haboozin, please be careful with this]

then you get X^2/25 + Y^2/(25/16) = 1

so, u get a^2 = 25, b^2 = 25/16, sub into a^2 = a^2e^2 + b^2, OR e^2 = (a^2 - b^2) / a^2

so e^2 = (25 - 25/16)/25 = 15/16

so e = sqrt 5 / 4.

hopefully joesmith1975 can do the rest from here.

 

[joesmith1975]

yere i just got it before yere post.

Thanks for the help

 

[haboozin]

[haboozin, please be careful with this]

yea, i read it again and im like.... hmmm i hope he doesnt confuse that to be 216 or something.