高等数学证明数列收敛和求出极限设a1=1,当n>=1时,a(n+1)=(an/1+an)^1/2,证明数列收敛并且求出其极限.
2019-04-14
高等数学证明数列收敛和求出极限
设a1=1,当n>=1时,a(n+1)=(an/1+an)^1/2,证明数列收敛并且求出其极限.
优质解答
a(n+1)=[an/(1+an)]^(1/2)
|an| > 0
{an} 递减
=> lim(n->∞)an exists
lim(n->∞)a(n+1)=lim(n->∞)[an/(1+an)]^(1/2)
L= (L/(1+L))^(1/2)
L^2(1+L) = L
L(L^2+L -1) =0
L = (-1+√5)/2
lim(n->∞)an =L =(-1+√5)/2
a(n+1)=[an/(1+an)]^(1/2)
|an| > 0
{an} 递减
=> lim(n->∞)an exists
lim(n->∞)a(n+1)=lim(n->∞)[an/(1+an)]^(1/2)
L= (L/(1+L))^(1/2)
L^2(1+L) = L
L(L^2+L -1) =0
L = (-1+√5)/2
lim(n->∞)an =L =(-1+√5)/2