Which expression gives the length of the transverse axis of the hyperbola
shown below?

Explanation:

Length of transverse axis of hyperbola means distance between both the vertices of hyperbola which is constant given by 2a.

As definition of hyperbola:

Difference in distance of any point (x,y) from both focus is a positive constant equals to length of transverse axis.

So, distance of (x,y) from foci 1)-( distance of (x,y) from foci 2)=2a

x-y=2a

Length of transverse axis is x-y.

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