解：?$(1)$?把?$x=0、$??$y=2、$??$h=2.6$?代入?$y=a(x-6)^2+h，$?
即?$2=a(0-6)^2+2.6$?
∴?$a=- \frac {1}{60}$?
∴?$y=- \frac {1}{60} (x-6)^2+2.6$?
?$(2) $?當(dāng)?$h=2.6$?時(shí)，?$y=-\frac {1}{60} (x-6)^2+2.6，$?
當(dāng)?$x=9$?時(shí)，?$y=-\frac {1}{60} (9-6)^2+2.6=2.45>2.43$?
∴球能越過網(wǎng)
當(dāng)?$x=18$?時(shí)，?$y=- \frac {1}{60} (18-6)^2+2.6=0.2> 0$?
∴球會出界
