Question

заранее спасибо! ;-)​

Answer 1

$x^{4}-4x^{2}-45=0\\\\x^{2} =m,m\geq0\\\\m^{2}-4m-45=0\\\\D=(-4)^{2} -4*(-45)=16+180=196=14^{2}\\\\m_{1}=\frac{4+14}{2}=9\\\\m_{2}=\frac{4-14}{2} =-5<0-neyd\\\\x^{2}=9\\\\x_{1}=-3\\\\x_{2}=3\\\\Otvet:\boxed{-3;3}$