We may determine the degree of a polynomial by observing the number of times it has intersected the x-axis
Above in the picture we can tell that it has intersection coordinates of
((-2,0) (-1,0) (1,0)(2,0)
Therefore we have a 4th-degree polynomial (which makes it even degree)
And since both of his sides are going infinitely upwards then the leading coefficient is positive.
Hope i helped.