We will use factoring:[tex] x^{4} -5 x^{2} -14 = 0 \\ x^{4} -7 x^{2} +2 x^{2} -14 =0 \\ x^{2} ( x^{2} -7)
+2( x^{2} -7)=0 \\
( x^{2} -7)( x^{2} +2)=0
[/tex]
x² - 7 = 0
x² = 7
x = [tex] \sqrt{7} [/tex]
or x=[tex] -\sqrt{7} [/tex]
x² + 2 = 0
x² = - 2, this part of equation has no solutions.
