x轴上点列 p0(x0,0) p1(x1,0) ...满足向量pnp(n+2)=λpnp(n+1)
1个回答

(1)

pnp[n+2]=λpnp[n+1]

即(Xn,0)(X[n+2],0)=λ(Xn,0)(X[n+1],0)

即XnX[n+2]=λXnX[n+1]

即X[n+2]=λX[n+1]

X[n+2]/X[n+1]=λ

an=X[n+1]-Xn

a[n+1]=X[n+2]-X[n+1]=λX[n+1]-X[n+1]=(λ-1)X[n+1]

a[n+2]/a[n+1]=((λ-1)X[n+2])/((λ-1)X[n+1])=X[n+2]/X[n+1]=λ

∴{an}为等比数列,公比q=λ.首项a1=(λ-1)X1=λ-1

∴an=a1q^n=(λ-1)λ^n

(2)pn横坐标 即求Xn

∵由(1)已证

a[n+1]=X[n+2]-X[n+1]=λX[n+1]-X[n+1]=(λ-1)X[n+1]

∴an=(λ-1)Xn=(λ-1)λ^n

∴Xn=λ^n