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The first lesson of mathematics arrangement in senior two.
Answer: 1)∵ Left =A(m, n)=(n! )/(n-m)!

Right =[n*(n- 1)! ]/[(n- 1)-(m- 1)]!

=n! /(n-m)! ,

∴ A(m,n)=nA(m- 1,n- 1)

2)、A(8,8)-8*A(7,7)+7*A(6,6)

=8! -8*7! +7*6!

=8! -8! +7!

=7!

=A(7,7)

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