Não há uma solução fácil de ser calculada. Pela aproximação de Newton, obtemos (análise Numérica):
n ##### xn #################### f(xn) #################### f'(xn) #################### x(n+1)
1 ##### 5,000000000 ########## 2,236067977 ########## 10,2236068 ########## 4,781283844
2 ##### 4,781283844 ########## 0,047289898 ########## 9,791231659 ########## 4,776454023
3 ##### 4,776454023 ########## 2,30481E-05 ########## 9,781687597 ########## 4,776451667
4 ##### 4,776451667 ########## 5,48539E-12 ########## 9,781682941 ########## 4,776451667
5 ##### 4,776451667 ########## 0000000000 ########## 9,781682941 ########## 4,776451667
x = 4,776451667
Utilizado:
Eu faço a diferença. E você?
Do Poema: Quanto os professores "fazem"?
De Taylor Mali
![{x}^{2} + \sqrt[]{x} - 25 = 0](/latexrender/pictures/c9f3b898c1be36d626990445eb50831c.png "{x}^{2} + \sqrt[]{x} - 25 = 0")
por Claudio Matos » Ter Ago 18, 2015 15:43 
![\frac{\sqrt[]{\sqrt[4]{8}+\sqrt[]{\sqrt[]{2}-1}}-\sqrt[]{\sqrt[4]{8}-\sqrt[]{\sqrt[]{2}-1}}}{\sqrt[]{\sqrt[4]{8}-\sqrt[]{\sqrt[]{2}+1}}}](/latexrender/pictures/981987c7bcdf9f8f498ca4605785636a.png "\frac{\sqrt[]{\sqrt[4]{8}+\sqrt[]{\sqrt[]{2}-1}}-\sqrt[]{\sqrt[4]{8}-\sqrt[]{\sqrt[]{2}-1}}}{\sqrt[]{\sqrt[4]{8}-\sqrt[]{\sqrt[]{2}+1}}}")
![\sqrt[]{2}](/latexrender/pictures/f21662d1cabab6e8b273a4b6f1cd663a.png "\sqrt[]{2}")
(dica : igualar a expressão a 
e elevar ao quadrado os dois lados)