(1)设C(a,1/2a+2)
1/2(a+4)(1/2a+2)=9
a+4=6或-6
a=2或-10
C(2,3)或(-10,-3)
双曲线y=6/x或y=30/x
(2)E(3,2)或(-3,-2)或(-3,-10)(3,10)