Question

х^4 + 5х^2 – 36 = 0. x^2=?

Answer 1

$x^4+5x^2-36=0\\t:=x^2 geq 0\\t^2+5t-36=0\t_1=-9<0;quad t_2=4$

первый корень не удовл.

x^2=4