How do you classify the conic #3x^2+y^2+2x+2y=0#?

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Answer 1 · 2017-01-20T08:18:32

#3x^2+y^2+2x+2y=0# is an ellipse.

Let the equation be of the type #Ax^2+Bxy+Cy^2+Dx+Ey+F=0#

then if

#B^2-4AC=0# and #A=0# or #C=0#, it is a parabola

#B^2-4AC<0# and #A=C#, it is a circle

#B^2-4AC<0# and #A!=C#, it is an ellipse

#B^2-4AC>0#, it is a hyperbola

In the given equation #3x^2+y^2+2x+2y=0#

#A=3#, #B=0# and #C=1#

Therefore, #B^2-4AC=0^2-4xx3xx1=-12<0# and #A!=C#

Hence, #3x^2+y^2+2x+2y=0# is an ellipse.
graph{3x^2+y^2+2x+2y=0 [-2.55, 2.45, -2.2, 0.3]}