Question

在等差数列｛An｝中,已知Ap=q,Aq=p(p不等于q),求Ap+q

Answer 1

设等差数列首项为A(1),公差为d,则

A(p)=A(1)+(p-1)d=q,

A(q)=A(1)+(q-1)d=p,

解得A(1)=p+q-1,d=-1,

A(p+q)=a(1)+(p+q-1)d=0.