The sum of the distances from point m to point a (4,0) and point B (- 4,0) is 12. Find the trajectory equation of point M Trouble to write out the process, I was a little bit of calculation that trouble

The sum of the distances from point m to point a (4,0) and point B (- 4,0) is 12. Find the trajectory equation of point M Trouble to write out the process, I was a little bit of calculation that trouble

2a=12,c=4,a=6,b^2=a^2-c^2=20
x^2/36+y^2/20=1