∵ Point A is on the inverse proportional function image, ∴a(- 12a+m)=k, that is, k=- 12a2+am.

C(2m, 0) can be obtained from the resolution function,

∴CE=2m-a，

∴OE.CE=a(2m-a)=-a2+2am= 12，

∴k= 12(-a2+2am)= 12× 12=6.

(2) Proof: connecting AF and BE, through E and F are FM⊥AB and EN⊥AB respectively.

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