From the ellipse equation
[tex]\frac{(x+h)^2}{a^2}+\frac{(y+k)^2}{b^2}=1[/tex]
the length of the major axis is equal to 2a. By comparing this equation with the given one, we can note that
[tex]\begin{gathered} a=7 \\ \text{because} \\ 7^2=49 \end{gathered}[/tex]
Then, the length of the major axis is 2x7 = 14
