y=x^2+10cosx
y'=2x-10sinx
x(n+1)=(2xn-10sinxn)/(xn^2+10cosxn)
y是偶函数,所以两个解是相反数
假设x1=2
x2=2.2452
x3=1.8828
x4=1.9654
x5=1.9689
x6=1.9689
所以x=±1.9689