(1)
A={a^2,a+2,-3},B={a-3,2a-1,a^2,1};A∩B={-3}
A∩B={-3}
=> a-3 = -3 or 2a-1 = -3
=> a = 0 or a = -1
if a=0
A∪B = { 0,2,-3,-1,1 }
if a= -1
a^2 = 1
a+2 = 1 = a^2
(rejected)
therefore
A∪B = { 0,2,-3,-1,1 }
(2)
A={x|-x^2+3x>0}
= { x | x(x-3) a+3 < 0 or -a+3 > 3
=> a < -3 or a < 0
（rejected）
ie a≤ 0,A∩B= ø