如果单项式2ax的m次方y与单项式5bx2m-3的次方y的和是0,且xy不等于0,求（2a+5b)的2007m次方的值.
2ax^m *y+5bx^(2m-3)* y=0
2ax^m y=-5bx^(2m-3 )y
2ax^m =-5bx^(2m-3 )
得2a=-5b
x^m =x^2m-3
m=2m-3
m=3
(2a+5b)^2007m=0