The center is (0, 0) and the length of half the x-axis is 3. The length of half the y-axis is 2, so the equation can be written as
[tex] ( \frac{x}{3 )^{2} + ( \frac{y}{2} )^{2} = 1 [/tex]
Multiplying by 36 gives you
[tex] 4 x^{2} + 9 y^{2} = 36 [/tex] . . . . . corresponding to the 3rd selection
