mx^2+5y^2=5m
x^2/5+y^2/m=1
a^2=5,b^2=m or a^2=m ,b^2=5
c^2=5-m or c^2=m-5
(c/a)^2=(5-m)/5 or (c/a)^2=(m-5)/m
10/25=(5-m)/5 or 10/25=(m-5)/m
2=5-m or 2m=5m-25
m=3 or m=25/3