Question

Which of the following equations describes an ellipses?
a) 25x^(2)+16y^(2)-50x-96y-231=0
b) 9x^(2)+y^(2)+54x-2y+73=0
c) 16x^(2)+25y^(2)-64x-150y-111=0
d) 25x^(2)+9y^(2)-72y-81=0
e) 4y^(2)-x^(2)-32y-4y+56=0

Answer 1

*there can be more than one answer

Answer 2

if ab>0, the equation is an ellipse

Answer 3

where a is the coeff of x^2 and b the coeff of y^2

Answer 4

I know it is an ellipse, but which equation describes it?

Answer 5

i said calculate ab for every case

Answer 6

and then when ab is negative..its an ellipse

Answer 7

so only e) is an ellipse

Answer 8

wouldn't e add up to a possitive though?

Answer 9

i didnt tell u to add..multiply a and b

Answer 10

or do you not go by the result of the two, but the fact that one of the factors is negative

Answer 11

nvm i got it. thank you.

Answer 12

in e) a x b is negative