x^2/4+y^2/9=1
a^2=9,b^2=4
所以c^2=5
所以假设所求的是x^2/m^2+y^2/n^2=1
则n^2-m^2=5
x^2/m^2+y^2/(m^2+5)=1
过点(2,-3)
4/m^2+9/(m^2+5)=1
9m^2+4(m^2+5)=m^2(m^2+5)
m^2=10,m^2=-2(舍去)
x^2/10+y^2/15=1