Question 83304
Given equation of the ellipse is 3x^2 + 4y^2 = 12

Dividing by 12 throughout,

3x^2/12 + 4y^2/12 = 12/12

==>  x^2/4 + y^2/3 = 1

This is of the form x^2/a^2  + y^2/b^2 = 1

On comparing we get a = 2

So length of major axis = 2a

                        = 4